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Standards
- 1: OpenAPI
- 2: OpenAPI Overlays
- 3: Arazzo
- 4: AsyncAPI
- 5: APIOps Cycles
- 6: Postman Collections
- 7: Postman Environments
- 8: Backstage Software Catalog Format
- 9: Bruno Collection
- 10: Bruno Environment
- 11: Open Collections
- 12: gRPC
- 13: JSON RPC
- 14: Model Context Protocol (MCP)
- 15: Apache Parquet
- 16: Avro
- 17: Agent2Agent
- 18: JSON Schema
- 19: Protocol Buffers
- 20: Schema.org
- 21: JSON-LD
- 22: Spectral
- 23: Vacuum
- 24: Open Policy Agent (OPA)
- 25: CSV
- 26: HTML
- 27: Java Database Connectivity (JDBC)
- 28: JSON
- 29: Markdown
- 30: ODBC
- 31: YAML
- 32: XML
- 33: OAuth 2.0
- 34: JSON Web Token (JWT)
- 35: HTTP
- 36: HTTP 2.0
- 37: HTTP 3.0
- 38: APIs.json
- 39: API Commons
- 40: Microcks Examples
- 41: vCard Ontology
1 - OpenAPI
Describing the surface area of HTTP APIs and Webhooks.
The OpenAPI Specification (OAS) is a formal standard for describing HTTP APIs. It enables teams to understand how an API works and how multiple APIs interoperate, generate client code, create tests, apply design standards, and more.
OpenAPI was formerly known as Swagger. In 2015, SmartBear donated the specification to the Linux Foundation, establishing the OpenAPI Initiative (OAI) and a formal, community-driven governance model that anyone can participate in.
An OpenAPI document can be written in JSON or YAML and typically defines elements such as: Info, Contact, License, Servers, Components, Paths and Operations, Parameters, Request Bodies, Media Types and Encoding, Responses, Callbacks, Examples, Links, Headers, Tags, Schemas, and Security.
OpenAPI has an active GitHub organization, blog, LinkedIn page, and Slack channel to encourage community participation. In addition, OAI membership helps fund projects and events that drive awareness and adoption.
The OpenAPI Specification can be used alongside two other OAI specifications: (1) the Arazzo specification for defining API-driven workflows, and (2) OpenAPI Overlays, which allow additional information to be overlaid onto an OpenAPI document.
License: Apache
Tags: HTTP APIs, Webhooks
Properties: Info, Contact, License, Servers, Components, Paths and Operations, Parameters, Request Bodies, Media Types and Encoding, Responses, Callbacks, Examples, Links, Headers, Tags, Schemas, and Security
Website: https://www.openapis.org
2 - OpenAPI Overlays
Define metadata, operations, and data structures for overlaying on top of OpenAPI.
The Overlay Specification is an auxiliary standard that complements the OpenAPI Specification. An OpenAPI description defines API operations, data structures, and metadata—the overall shape of an API. An Overlay lists a series of repeatable changes to apply to a given OpenAPI description, enabling transformations as part of your API workflows.
OpenAPI Overlays emerged from the need to adapt APIs for varied use cases, from improving developer experience to localizing documentation. The first version was recently released, and the roadmap is being developed within the OpenAPI Initiative.
The specification provides three constructs for augmenting an OpenAPI description: Info, Overlays, and Actions. How these are applied is being worked out across different tools and industries to accommodate the diversity of APIs being delivered.
To get involved, participate via the GitHub repository, where you’ll find discussions, meeting notes, and related topics. There’s also a dedicated channel within the broader OpenAPI Initiative Slack.
OpenAPI Overlays offer a robust way to manage the complexity of producing and consuming APIs across industries, regions, and domains. As the specification matures, it presents a strong opportunity to ensure documentation, mocks, examples, code generation, tests, and other artifacts carry the right context for different situations.
License: Apache License
Tags: Overlays
Properties: info, overlays, and actions
Website: https://spec.openapis.org/overlay/v1.0.0.html
Standards: JSON Schema
3 - Arazzo
Describing your business processes and workflows using OpenAPI.
The Arazzo Specification is a community-driven, open standard within the OpenAPI Initiative (a Linux Foundation Collaborative Project). It defines a programming-language-agnostic way to express sequences of calls and the dependencies between them to achieve a specific outcome.
Arazzo emerged from a need identified in the OpenAPI community for orchestration and automation across APIs described with OpenAPI. Version 1 of the specification is available, and work on future iterations is guided by a public roadmap.
With Arazzo, you can define elements such as: Info, Sources, Workflows, Steps, Parameters, Success Actions, Failure Actions, Components, Reusables, Criteria, Request Bodies, and Payload Replacements—providing a consistent approach to delivering a wide range of automation outcomes.
You can engage with the Arazzo community via the GitHub repository for each version and participate in GitHub Discussions to stay current on meetings and interact with the specification’s stewards and the broader community.
Arazzo is the logical layer on top of OpenAPI: it goes beyond documentation, mocking, and SDKs to focus on defining real business workflows that use APIs. Together, Arazzo and OpenAPI help align API operations with the rest of the business.
License: Apache 2.0
Tags: Workflows, Automation
Properties: Info, Source, Workflows, Steps, Parameters, Success Actions, Failure Actions, Components, Reusable, Criterion, Request Bodies, and Payload Replacements
4 - AsyncAPI
Describing the surface area of your event-driven infrastructure.
AsyncAPI is an open-source, protocol-agnostic specification for describing event-driven APIs and message-driven applications. It serves as the OpenAPI of the asynchronous, event-driven world—overlapping with, and often going beyond, what OpenAPI covers.
The specification began as an open-source side project and was later donated to the Linux Foundation after the team joined Postman, establishing it as a standard with formal governance.
AsyncAPI lets you define servers, producers and consumers, channels, protocols, and messages used in event-driven API operations—providing a common, tool-friendly way to describe the surface area of event-driven APIs.
To get involved, visit the AsyncAPI GitHub repository and blog, follow the LinkedIn page, tune into the YouTube or Twitch channels, and join the conversation in the community Slack.
AsyncAPI can be used to define HTTP APIs much like OpenAPI, and it further supports multiple protocols such as Pub/Sub, Kafka, MQTT, NATS, Redis, SNS, Solace, AMQP, JMS, and WebSockets—making it useful across many approaches to delivering APIs.
License: Apache
Tags: Event-Driven
Properties: Servers, Producers, Consumers, Channels, Protocols, and Messages
Website: https://www.asyncapi.com
5 - APIOps Cycles
Aligning engineering with products when it comes to APIs.
The method is built around a collection of strategic canvas templates that help teams systematically address everything from customer journey mapping and value proposition definition to domain modeling, capacity planning, and risk assessment. As an open-source framework released under the Creative Commons Attribution–ShareAlike 4.0 license, APIOps Cycles is freely available for anyone to use, adapt, and share, with the complete method consisting of localized JSON and markdown files that power both the official website and open tooling available as an npm package. Whether you’re a developer integrating the method into your products and services, or an organization seeking to establish API product strategy and best practices, APIOps Cycles offers a proven, community-backed approach supported by a network of partners who can provide guidance and expertise in implementing the methodology effectively.
License: Creative Commons Attribution–ShareAlike 4.0
Tags: Products, Operations
Website: https://www.apiopscycles.com/
APIOps Cycles Canvases Outline
- Customer Journey Canvas
- Persona
- Customer Discovers Need
- Customer Need Is Resolved
- Journey Steps
- Pains
- Gains
- Inputs & Outputs
- Interaction & Processing Rules
- API Value Proposition Canvas
- Tasks
- Gain Enabling Features
- Pain Relieving Features
- API Products
- API Business Model Canvas
- API Value Proposition
- API Consumer Segments
- Developer Relations
- Channels
- Key Resources
- Key Activities
- Key Partners
- Benefits
- Costs
- Domain Canvas
- Selected Customer Journey Steps
- Core Entities & Business Meaning
- Attributes & Business Importance
- Relationships Between Entities
- Business, Compliance & Integrity Rules
- Security & Privacy Considerations
- Interaction Canvas
- CRUD Interactions
- CRUD Input & Output Models
- CRUD Processing & Validation
- Query-Driven Interactions
- Query-Driven Input & Output Models
- Query-Driven Processing & Validation
- Command-Driven Interactions
- Command-Driven Input & Output Models
- Command-Driven Processing & Validation
- Event-Driven Interactions
- Event-Driven Input & Output Models
- Event-Driven Processing & Validation
- REST Canvas
- API Resources
- API Resource Model
- API Verbs
- API Verb Example
- GraphQL Canvas
- API Name
- Consumer Goals
- Key Types
- Relationships
- Queries
- Mutations
- Subscriptions
- Authorization Rules
- Consumer Constraints
- Notes / Open Questions
- Event Canvas
- User Task / Trigger
- Input / Event Payload
- Processing / Logic
- Output / Event Result
- Capacity Canvas
- Current Business Volumes
- Future Consumption Trends
- Peak Load and Availability Requirements
- Caching Strategies
- Rate Limiting Strategies
- Scaling Strategies
- Business Impact Canvas
- Availability Risks
- Mitigate Availability Risks
- Security Risks
- Mitigate Security Risks
- Data Risks
- Mitigate Data Risks
- Locations Canvas
- Location Groups
- Location Group Characteristics
- Locations
- Location Characteristics
- Location Distances
- Location Distance Characteristics
- Location Endpoints
- Location Endpoint Characteristics
6 - Postman Collections
Executable artifact for automating APi requests and responses for testing.
A Postman Collection is a portable JSON artifacts that organizes one or more API requests—plus their params, headers, auth, scripts, and examples—so you can run, share, and automate them in the Postman desktop or web client application. Collections can include folders, collection- and environment-level variables, pre-request and test scripts, examples, mock server definitions, and documentation.
Postman Collections started as a simple way to save and share API requests in the early Postman client (2013), then grew into a formal JSON format with the v1 schema published in 2015. The format then stabilized as v2.0.0 and shortly after as v2.1.0 in 2017, which remains the common export/import version today.
Owner: Postman
License: Apache 2.0
Properties: Metadata, Requests, Scripts, Variables, Authentication, Methods, Headers, URLs, Bodies, Events, Responses
Website: https://postman.com
7 - Postman Environments
Storing variables for running along with Postman Collections.
Postman environments are a powerful feature that allow you to manage different sets of variables for your API testing and development workflow. An environment is essentially a named collection of key-value pairs (variables) that you can switch between depending on your context—such as development, staging, or production. For example, you might have different base URLs, authentication tokens, or API keys for each environment. Instead of manually updating these values in every request when you switch from testing locally to hitting a production server, you can simply select a different environment from a dropdown menu, and all your requests will automatically use the appropriate variables. This makes it much easier to maintain consistency, avoid errors, and streamline your workflow when working across multiple environments or sharing collections with team members.
Owner: Postman
License: Apache 2.0
Properties: Variables, Variable name, Initial value, Current value, Type, Environment Name, Environment ID, Scope, State
Website: https://learning.postman.com/docs/sending-requests/variables/managing-environments/
8 - Backstage Software Catalog Format
The core catalog format for the Backstage environment.
The Backstage Software Catalog provides a centralized system for registering, organizing, and discovering software components across an organization. By using a standardized, YAML-based format, it captures metadata such as ownership, dependencies, lifecycle stage, documentation links, and operational context for services, APIs, libraries, and infrastructure resources. This allows teams to understand how systems fit together, who is responsible for them, and how they should be operated, while enabling automation, governance, and consistent developer experiences through a single, searchable developer portal.
Website: https://backstage.io/docs/features/software-catalog/descriptor-format/
9 - Bruno Collection
Open source client specification.
Bruno collections are structured groups of API requests, variables, and environments used within the Bruno API client to help developers organize and manage their API workflows. Each collection acts as a self-contained workspace where you can store requests, define authentication, set environment values, document behaviors, and run tests. Designed with a filesystem-first approach, Bruno collections are easy to version-control and share, making them especially useful for teams collaborating on API development or maintaining consistent testing practices across environments.
License: MIT license
Tags: Clients, Executable
Properties: Name, Type, Version, Description, Variables, Environment, Folders, Requests, Auth, Headers, Scripts, Settings
Website: https://www.usebruno.com/
10 - Bruno Environment
A open-source client environment.
A Bruno environment is a configurable set of key–value variables that allows you to run the same API requests across different deployment contexts, such as local development, staging, and production. Environments typically store values like base URLs, authentication tokens, headers, or other parameters that may change depending on where an API is being tested. By separating these values from the requests themselves, Bruno makes it easy to switch contexts, maintain cleaner collections, and ensure consistency when collaborating with others or automating API workflows.
License: MIT license
Tags: Name, Variables, Enabled, Secret, Ephemeral, Persisted Value
Properties: Name, Type, Version, Description, Variables, Environment, Folders, Requests, Auth, Headers, Scripts, Settings
Website: https://www.usebruno.com/
11 - Open Collections
Open-source collection format.
The OpenCollection Specification is a format for describing API collections, including requests, authentication, variables, and scripts. This specification enables tools to understand and work with API collections in a standardized way.
License: Apache License
Tags: Collections
Website: https://www.opencollection.com/
12 - gRPC
Communicating the interoperability between systems using AI agents.
The Agent2Agent (A2A) Protocol is an open standard for communication and interoperability among independent—often opaque—AI agent systems. Because agents may be built with different frameworks, languages, and vendors, A2A provides a common language and interaction model.
License: Apache 2.0
Tags: agents
Properties: client, servers, cards, messages, tasks, part, artifacts, streaming, push notifications, context, etensions, transport, negotiation, authentication, authorization, and discovery for agent automation. A2A has the discovery, network, context
Website: https://a2a-protocol.org/latest/
Standards: JSON-RPC 2.0, gRPC
13 - JSON RPC
Lightweight transport-agnostic remote procedure call protocol.
JSON-RPC is a lightweight, transport-agnostic remote procedure call (RPC) protocol that uses JSON to encode requests and responses: a client sends an object with jsonrpc:“2.0”, a method name, optional params (positional or named), and an id; the server replies with either a result or an error (including standardized error codes), and it also supports notifications (no id, no response) and request batching.
JSON-RPC emerged in the mid-2000s as a community-driven, lightweight RPC protocol using JSON, with an informal 1.0 spec (c. 2005) that defined simple request/response messaging and “notifications” (no reply). A 1.1 working draft (around 2008) tried to broaden and formalize features but never became canonical. The widely adopted JSON-RPC 2.0 specification (2010) simplified and standardized the model—introducing the mandatory “jsonrpc”:“2.0” version tag, clearer error objects, support for both positional and named parameters, and request batching—while remaining transport-agnostic (HTTP, WebSocket, pipes, etc.).
License: Apache License 2.0 or MIT License
Tags: RPC
Properties: methods, parameters, identifier, results, errors, codes, messages, data
Website: https://www.jsonrpc.org/
Forum:** https://groups.google.com/g/json-rpc
14 - Model Context Protocol (MCP)
Allowing applications to connect to large language models (LLMs).
MCP (Model Context Protocol) is an open protocol that standardizes how applications provide context to large language models (LLMs). It offers a consistent way to connect AI models to diverse data sources and tools, enabling agents and complex workflows that link models to the outside world.
Introduced by Anthropic as an open-source effort, MCP addresses the challenge of integrating AI models with external tools and data. It aims to serve as a universal “USB port” for AI, allowing models to access real-time information and perform actions.
MCP defines concepts and properties such as hosts, clients, servers, protocol negotiation, lifecycle, transports, authorization, resources, prompts, tools, sampling, roots, elicitation, progress, cancellation, errors, and logging—providing a standardized approach to connecting applications with LLMs.
The MCP community organizes around a GitHub repository (with issues and discussions), plus a Discord, blog, and RSS feed to track updates and changes to the specification.
MCP is seeing growing adoption among API and tooling providers for agent interactions. Many related API/AI specifications reference, integrate with, or overlap with MCP—despite the project being an open-source protocol currently stewarded by a single company, which has not been contributed to a foundation.
Owner: Anthropic
License: MIT License
Tags: agents, workflows
Properties: hosts, clients, servers, protocols, negotiation, lifecycle, transports, authorization, resources, prompts, tools, sampling, roots, elicitation, progress, cancellation, errors, logging
Website: https://modelcontextprotocol.io/
Standards: JSON-RPC 2.0, JSON Schema
15 - Apache Parquet
Compact binary data serialization.
Apache Parquet is a columnar storage file format specifically designed for efficient data storage and processing in big data analytics environments, developed as a collaboration between Twitter and Cloudera in 2013 and now part of the Apache Software Foundation. Unlike traditional row-oriented formats (like CSV or Avro) that store data records sequentially, Parquet organizes data by columns, grouping all values from the same column together in storage. This columnar approach provides significant advantages for analytical workloads where queries typically access only a subset of columns from wide tables—instead of reading entire rows and discarding unneeded columns, Parquet allows systems to read only the specific columns required for a query, dramatically reducing I/O operations and improving query performance. The format also enables highly effective compression since values in the same column tend to have similar characteristics and patterns, allowing compression algorithms like Snappy, Gzip, LZO, and Zstandard to achieve much better compression ratios than they would on mixed-type row data. Parquet files are self-describing, containing schema information and metadata that allow any processing system to understand the data structure without external schema definitions.
Parquet has become the de facto standard for analytical data storage in modern data lakes and big data ecosystems, with native support across virtually all major data processing frameworks including Apache Spark, Apache Hive, Apache Impala, Presto, Trino, Apache Drill, and cloud data warehouses like Amazon Athena, Google BigQuery, Azure Synapse, and Snowflake. The format supports rich data types including nested and repeated structures (arrays, maps, and complex records), making it ideal for storing semi-structured data from JSON or Avro sources while maintaining query efficiency. Parquet’s internal structure uses techniques like dictionary encoding for low-cardinality columns, bit-packing for small integers, run-length encoding for repeated values, and delta encoding for sorted data, all of which contribute to both storage efficiency and query speed. The format includes column statistics (min/max values, null counts) stored in file metadata that enable predicate pushdown—allowing query engines to skip entire row groups or files that don’t contain relevant data based on filter conditions. This combination of columnar organization, advanced encoding schemes, efficient compression, predicate pushdown, and schema evolution support makes Parquet the optimal choice for data warehouse tables, analytical datasets, machine learning feature stores, time-series data, and any scenario where fast analytical queries over large datasets are required, often achieving 10-100x improvements in query performance and storage efficiency compared to row-oriented formats.
License: Apache 2.0
Tags: Data, Serialization, Binary
Properties: Columnar Storage Format, Column-Oriented, Apache Project, Open Source, Twitter-Cloudera Collaboration, Big Data Format, Analytics Optimized, Self-Describing, Schema Embedded, Metadata Rich, Binary Format, Efficient Storage, High Compression, Compression Support, Snappy Compression, Gzip Compression, LZO Compression, Brotli Compression, Zstandard Compression, Uncompressed Option, Column-Level Compression, Encoding Schemes, Dictionary Encoding, Run-Length Encoding, Bit-Packing, Delta Encoding, Delta Binary Packing, Plain Encoding, Byte Stream Split, Hybrid Encoding, Efficient Reads, Selective Column Access, Column Pruning, Projection Pushdown, Predicate Pushdown, Filter Pushdown, Statistics-Based Filtering, Row Group Skipping, Page-Level Statistics, Column Statistics, Min/Max Values, Null Counts, Distinct Counts, Bloom Filters, File-Level Metadata, Row Group Metadata, Column Chunk Metadata, Page Metadata, Schema Evolution, Schema Compatibility, Add Columns, Remove Columns, Rename Columns, Type Evolution, Nested Data Support, Complex Types, Struct Types, Array Types, Map Types, List Types, Repeated Fields, Optional Fields, Required Fields, Hierarchical Data, Semi-Structured Data, JSON Compatible, Avro Compatible, Thrift Compatible, Protocol Buffers Compatible, Rich Data Types, Primitive Types, Boolean Type, Integer Types, INT32, INT64, INT96, Float Type, Double Type, Binary Type, Fixed-Length Binary, String Type, UTF-8 Strings, Decimal Type, Date Type, Time Type, Timestamp Type, UUID Type, Enum Type, Logical Types, Converted Types, Annotation Support, Row Groups, Columnar Chunks, Data Pages, Dictionary Pages, Index Pages, Header Pages, Footer Structure, Magic Number, Version Number, File Format Version, Parquet Format 2.0, Apache Arrow Integration, Arrow Flight, In-Memory Format, Zero-Copy Reads, Memory Mapping, Lazy Loading, Streaming Reads, Batch Reads, Vectorized Processing, SIMD Optimization, CPU Efficiency, I/O Efficiency, Network Efficiency, Query Performance, Fast Scans, Aggregate Performance, Join Performance, Analytical Workloads, OLAP Queries, Data Warehouse Format, Data Lake Format, Cloud Storage Optimized, S3 Optimized, Azure Blob Compatible, Google Cloud Storage Compatible, HDFS Compatible, Object Storage, Distributed Storage, Splittable Files, Parallel Processing, Multi-Threaded Reads, Concurrent Access, Apache Spark Integration, Spark SQL, DataFrame Support, Dataset Support, PySpark Support, Apache Hive Integration, Hive Tables, HiveQL Support, Impala Support, Presto Support, Trino Support, Apache Drill Support, Dremio Support, ClickHouse Support, DuckDB Support, Snowflake Compatible, BigQuery Compatible, Redshift Spectrum, Athena Compatible, Azure Synapse, Databricks Support, EMR Support, Dataproc Compatible, AWS Glue, Data Catalog Integration, Table Format Support, Delta Lake, Apache Iceberg, Apache Hudi, Time Travel, ACID Transactions, Schema Registry, Metastore Integration, Partition Support, Partitioned Tables, Partition Pruning, Bucketing Support, Sorted Data, Clustered Data, Data Organization, File Organization, Directory Structure, Hive Partitioning, Key-Based Partitioning, Date Partitioning, ETL Integration, Data Pipelines, Batch Processing, Stream Processing, Real-Time Analytics, Apache Kafka Integration, Apache Flink Support, Streaming Writes, Micro-Batching, Change Data Capture, Incremental Updates, Upsert Support, Delete Support, Merge Support, Compaction, Small File Problem, File Consolidation, Optimization, Vacuum Operations, Machine Learning, Feature Store, Training Datasets, Model Input, Data Science, Pandas Integration, NumPy Compatible, Scikit-learn, TensorFlow Datasets, PyTorch DataLoader, Jupyter Notebooks, R Support, Julia Support, Command Line Tools, parquet-tools, parquet-cli, File Inspection, Schema Extraction, Row Count, File Size, Compression Ratio, Storage Metrics, Performance Metrics, Benchmark Results, Query Optimization, Cost-Based Optimization, Statistics Collection, Cardinality Estimation, Data Profiling, Data Quality, Data Validation, Type Safety, Schema Validation, Constraint Checking, Business Rules, Programming Language Support, Java Support, Scala Support, Python Support, C++ Support, Go Support, Rust Support, JavaScript Support, .NET Support, Arrow Parquet, PyArrow, FastParquet, parquet-cpp, parquet-mr, parquet-format, Specification, Open Standard, Vendor Neutral, Cross-Platform, Portable Format, Interoperability, Data Exchange, Data Sharing, Data Publishing, Open Data, Public Datasets, Reproducible Research, Version Control Friendly, Git LFS Compatible, Data Versioning, Data Lineage, Provenance Tracking, Audit Trails, Compliance Support, GDPR Compatible, Data Governance, Access Control, Encryption Support, Encryption at Rest, Column Encryption, Transparent Encryption, Security, Authentication, Authorization, Row-Level Security, Column Masking, Data Redaction, PII Protection, Sensitive Data, Anonymization, Pseudonymization, Production Ready, Enterprise Grade, Mission Critical, High Performance, Scalable, Petabyte Scale, Exabyte Scale, Large Datasets, Wide Tables, Deep Nesting, High Cardinality, Low Cardinality, Sparse Data, Dense Data, Time Series Data, Event Data, Log Data, Metrics Data, Sensor Data, IoT Data, Clickstream Data, User Behavior, Transaction Data, Financial Data, Scientific Data, Genomics Data, Weather Data, Geospatial Data, GIS Integration, Location Data, Coordinates, Spatial Queries, Temporal Queries, Historical Data, Archive Format, Cold Storage, Data Retention, Backup Format, Disaster Recovery, Long-Term Storage, Cost Optimization, Storage Savings, Cloud Cost Reduction, Bandwidth Savings, Compute Efficiency, Resource Optimization, Green Computing, Energy Efficient, Carbon Footprint, Sustainability, Industry Standard, Widely Adopted, Battle Tested, Mature Technology, Active Development, Community Support, Documentation, Examples, Tutorials, Best Practices, Design Patterns, Anti-Patterns, Troubleshooting, Debugging, Profiling Tools, Performance Tuning, Optimization Guides, Migration Tools, Conversion Tools, CSV to Parquet, JSON to Parquet, Avro to Parquet, ORC Alternative, Comparison Benchmarks, Format Selection, Use Case Specific, Analytics First, Write Once Read Many, WORM, Append-Only, Immutable Files, Idempotent Writes, Exactly-Once Semantics, Consistency, Durability, Reliability, Fault Tolerance, Error Handling, Data Integrity, Checksum Validation, CRC Checks, Corruption Detection, Self-Healing, Backward Compatible, Forward Compatible, Version Migration, Legacy Support, Modern Format, Future Proof, Ecosystem Integration, Tool Support, BI Tools, Tableau Support, Power BI, Looker, Qlik, Metabase, Superset, Grafana, Monitoring, Observability, Telemetry, Usage Tracking, Access Patterns, Query Patterns, Workload Analysis
Website: https://parquet.apache.org/
16 - Avro
Compact binary data serialization.
Apache Avro is a data serialization framework developed within the Apache Hadoop project that provides a compact, fast binary data format along with rich data structures and schema definitions. Created by Doug Cutting (the creator of Hadoop) in 2009, Avro addresses the need for efficient data serialization in big data ecosystems where massive volumes of data must be stored and transmitted efficiently. Unlike JSON or XML which use verbose text-based formats, Avro serializes data into a compact binary representation that significantly reduces storage requirements and network bandwidth while maintaining fast serialization and deserialization performance. Avro schemas are defined using JSON, making them human-readable and language-independent, and these schemas travel with the data (either embedded in files or referenced through a schema registry), ensuring that any system can correctly interpret the serialized data without prior knowledge of its structure. This self-describing nature makes Avro particularly valuable in distributed systems where different services written in different languages need to exchange data reliably.
One of Avro’s most powerful features is its robust support for schema evolution, which allows data schemas to change over time without breaking compatibility between producers and consumers of that data. Avro supports both forward compatibility (new code can read old data) and backward compatibility (old code can read new data) through features like default values for fields, optional fields, and union types. This makes it ideal for long-lived data storage and streaming systems where data structures evolve as business requirements change. Avro has become a cornerstone technology in the big data ecosystem, widely used with Apache Kafka for streaming data pipelines (where the Confluent Schema Registry manages Avro schemas), Apache Spark for data processing, Apache Hive for data warehousing, and as the serialization format for Hadoop’s remote procedure calls. Avro supports rich data types including primitive types (null, boolean, int, long, float, double, bytes, string), complex types (records, enums, arrays, maps, unions, fixed), and logical types (decimals, dates, timestamps), and provides code generation capabilities that create type-safe classes in languages like Java, C++, C#, Python, Ruby, and PHP. Its combination of compact binary encoding, strong schema support, language independence, and schema evolution capabilities makes Avro the preferred serialization format for many data-intensive applications, particularly in streaming architectures and data lakes.
License: Apache 2.0
Tags: Data, Serialization, Binary
Properties: Data Serialization System, Binary Format, Compact Encoding, Schema-Based, JSON Schema Definition, Self-Describing Data, Apache Project, Apache Hadoop Ecosystem, Doug Cutting Created, Open Source, Language-Independent, Platform-Independent, Cross-Language Support, Rich Data Structures, Schema Evolution, Forward Compatibility, Backward Compatibility, Full Compatibility, Default Values, Optional Fields, Field Addition, Field Deletion, Field Renaming, Union Types, Schema Resolution, Schema Registry Support, Confluent Schema Registry, Schema Versioning, Schema ID, Schema Discovery, Dynamic Typing, Static Typing, Code Generation, Type-Safe Classes, Java Support, C++ Support, C# Support, Python Support, Ruby Support, PHP Support, JavaScript Support, Perl Support, Haskell Support, Rust Support, Go Support, Primitive Types, Null Type, Boolean Type, Integer Types, Int Type, Long Type, Float Type, Double Type, Bytes Type, String Type, Complex Types, Record Type, Enum Type, Array Type, Map Type, Union Type, Fixed Type, Logical Types, Decimal Type, Date Type, Time Type, Timestamp Type, Duration Type, UUID Type, Nested Structures, Recursive Types, Named Types, Namespace Support, Documentation Fields, Aliases, Order Specification, File Format, Object Container Files, Data Files, Block-Based Storage, Compression Support, Deflate Compression, Snappy Compression, Bzip2 Compression, XZ Compression, Zstandard Compression, Sync Markers, Splittable Files, Hadoop Compatible, MapReduce Compatible, HDFS Storage, Distributed Storage, Big Data Processing, Streaming Data, Apache Kafka Integration, Kafka Serialization, Producer Support, Consumer Support, Apache Spark Integration, Spark SQL, DataFrame Support, Dataset Support, Apache Hive Integration, Hive Tables, Metastore Integration, Apache Flink Support, Apache Storm Integration, Data Pipeline, ETL Processes, Data Lakes, Data Warehousing, Message Queue Format, Event Sourcing, Log Aggregation, RPC Framework, Remote Procedure Calls, IDL Support, Interface Definition, Service Definition, Protocol Definition, Request/Response, Binary Protocol, Efficient Serialization, Fast Deserialization, Low Overhead, Small Payload Size, Network Efficient, Storage Efficient, Memory Efficient, CPU Efficient, Performance Optimized, High Throughput, Low Latency, Scalable, Version Control Friendly, Schema Registry, Centralized Schema Management, Schema Validation, Schema Compatibility Checking, Breaking Change Detection, Migration Support, Data Transformation, Schema Mapping, Type Conversion, Field Mapping, Data Migration Tools, Schema Tools, Command Line Tools, Avro Tools JAR, Schema Validation Tools, File Inspection, Data Inspection, JSON Conversion, Avro to JSON, JSON to Avro, File Reading, File Writing, Stream Processing, Batch Processing, Real-Time Processing, Container Format, Metadata Support, Custom Metadata, User Metadata, Codec Support, Encoding Options, Generic Records, Specific Records, Reflect Records, Dynamic Schema, Runtime Schema, Compile-Time Schema, Type Safety, Null Safety, Missing Field Handling, Extra Field Handling, Type Promotion, Numeric Promotion, String Encoding, UTF-8, Byte Arrays, Binary Data, Large Object Support, Chunked Data, Block Size Configuration, Buffer Management, Memory Allocation, Object Reuse, Object Pooling, Zero-Copy, Direct Buffers, NIO Support, Async IO, Streaming API, Iterator Support, Random Access, Sequential Access, Index Support, Projection Support, Column Pruning, Predicate Pushdown, Filter Support, Query Optimization, Partition Support, Sharding, Distribution, Replication, Fault Tolerance, Data Integrity, Checksum Support, CRC Validation, Error Detection, Error Handling, Exception Handling, Validation Rules, Constraint Enforcement, Business Rules, Industry Standard, Production Ready, Enterprise Grade, Mission Critical, High Availability, Disaster Recovery, Backup Format, Archive Format, Long-Term Storage, Cold Storage, Hot Storage, Warm Storage, Tiered Storage, Cloud Storage Compatible, S3 Compatible, Azure Blob Storage, Google Cloud Storage, Object Storage, Distributed File Systems, Network File Systems, Local File Systems, Database Storage, NoSQL Databases, Document Stores, Column Stores, Key-Value Stores, Time Series Databases, Graph Databases, Search Engines, Elasticsearch Support, Solr Support, Analytics Engines, Data Science, Machine Learning Datasets, Training Data, Feature Storage, Model Serialization, Experiment Tracking, MLflow Integration, Data Versioning, DVC Support, Data Lineage, Data Provenance, Audit Trails, Compliance, GDPR Support, Data Governance, Data Quality, Data Catalog, Metadata Management, Documentation, API Documentation, Schema Documentation, Field Documentation, Type Documentation, Example Data, Sample Files, Test Data, Mock Data, Debugging Tools, Profiling Tools, Performance Monitoring, Metrics Collection, Logging Support, Tracing, Observability, Monitoring Integration, Alerting, Community Support, Active Development, Regular Releases, Bug Fixes, Security Patches, Performance Improvements, Feature Additions, Backward Compatible Releases, Stable API, Mature Technology, Battle Tested, Widely Adopted, Industry Proven, Ecosystem Integration, Tool Support, IDE Plugins, Editor Support, Build Tool Integration, Maven Support, Gradle Support, SBT Support, NPM Packages, PyPI Packages, Package Managers, Dependency Management, Transitive Dependencies, Minimal Dependencies, Lightweight, Portable, Embeddable, Library Form, Framework Integration, Microservices, Service Mesh, Container Support, Docker Compatible, Kubernetes Support, Cloud Native, Serverless Compatible, Lambda Functions, Edge Computing, IoT Data, Sensor Data, Telemetry, Metrics, Events, Notifications, Webhooks, API Responses, Interoperability, Protocol Buffers Alternative, Thrift Alternative, MessagePack Alternative, BSON Alternative, Parquet Complementary, ORC Complementary, Specification, Standard Format, Open Standard, Vendor Neutral, Community Driven
Website: https://avro.apache.org/
17 - Agent2Agent
Communicating the interoperability between systems using AI agents.
The Agent2Agent (A2A) Protocol is an open standard for communication and interoperability among independent—often opaque—AI agent systems. Because agents may be built with different frameworks, languages, and vendors, A2A provides a common language and interaction model.
License: Apache 2.0
Tags: agents
Properties: client, servers, cards, messages, tasks, part, artifacts, streaming, push notifications, context, etensions, transport, negotiation, authentication, authorization, and discovery for agent automation. A2A has the discovery, network, context
Website: https://a2a-protocol.org/latest/
Standards: JSON-RPC 2.0, gRPC
18 - JSON Schema
Annotating and validating JSON artifacts.
JSON Schema is a vocabulary for annotating and validating JSON documents. It defines the structure, content, and constraints of data—often authored in either JSON or YAML—and can be leveraged by documentation generators, validators, and other tooling.
The specification traces back to early proposals by Kris Zyp in 2007 and has evolved through draft-04, draft-06, and draft-07 to the current 2020-12 release.
JSON Schema provides a rich set of keywords—such as title, description, type, properties, required, additionalProperties, minimum, maximum, exclusiveMinimum, exclusiveMaximum, default, enum, pattern, items, allOf, anyOf, oneOf, not, examples, and $ref—to describe and validate data used in business operations.
To get involved with the community, visit the JSON Schema GitHub organization, subscribe to the blog via RSS, join discussions and meetings in the Slack workspace, and follow updates on LinkedIn.
JSON Schema is a foundational standard used by many other specifications, tools, and services. It’s the workhorse for defining and validating the digital data that keeps modern businesses running.
License: Academic Free License version 3.0
Tags: Schema, Validation
Properties: schema, title, description, type, properties, required, additionalProperties, minimum, maximum, exclusiveMinimum, exclusiveMaximum, default, enum, pattern, items, allOf, anyOf, oneOf, not, examples, and $ref
Website: https://json-schema.org
19 - Protocol Buffers
Fast binary serialized structured data.
Protocol Buffers (protobuf) are Google’s language-neutral, platform-neutral way to define structured data and serialize it efficiently (small, fast). You write a schema in a .proto file, generate code for your language (Go, Java, Python, JS, etc.), and use the generated classes to read/write binary messages.
Protocol Buffers began inside Google in the early 2000s as an internal, compact, schema-driven serialization format; in 2008 Google open-sourced it as proto2. Most recently in 2023, Google introduced “Protobuf Editions” to evolve semantics without fragmenting the language into proto2 vs. proto3, while the project continues to refine tooling, compatibility guidance, and release processes across a broad open-source community.
Owner: Google
License: BSD-3-Clause License
Tags: Schema, Data, Binary, Serialization
Properties: messages, types, fields, cardinality, comments, reserved values, scalars, defaults, enumerations, nested types, vinary, unknown fields, oneOf, maps, packages, and services
Website: https://protobuf.dev/
20 - Schema.org
Community-driven schema vocabulary for people, places, and things.
Schema.org is a collaborative, community-driven vocabulary that defines shared types and properties to describe things on the web—people, places, products, events, and more—so search engines and other consumers can understand page content. Publishers annotate pages using formats like JSON-LD (now the common choice), Microdata, or RDFa to express this structured data, which enables features such as rich results, knowledge panels, and better content discovery. The project maintains core and extension vocabularies, evolves through open proposals and discussion, and focuses on practical, interoperable semantics rather than being tied to a single standard body.
License: Creative Commons Attribution-ShareAlike License (CC BY-SA 3.0)
Tags: Schema
Properties: Thing, Action, AchieveAction, LoseAction, TieAction, WinAction, AssessAction, ChooseAction, VoteAction, IgnoreAction, ReactAction, AgreeAction, DisagreeAction, DislikeAction, EndorseAction, LikeAction, WantAction, ReviewAction, ConsumeAction, DrinkAction, EatAction, InstallAction, ListenAction, PlayGameAction, ReadAction, UseAction, WearAction, ViewAction, WatchAction, ControlAction, ActivateAction, AuthenticateAction, DeactivateAction, LoginAction, ResetPasswordAction, ResumeAction, SuspendAction, CreateAction, CookAction, DrawAction, FilmAction, PaintAction, PhotographAction, WriteAction, FindAction, CheckAction, DiscoverAction, TrackAction, InteractAction, BefriendAction, CommunicateAction, AskAction, CheckInAction, CheckOutAction, CommentAction, InformAction, ConfirmAction, RsvpAction, InviteAction, ReplyAction, ShareAction, FollowAction, JoinAction, LeaveAction, MarryAction, RegisterAction, SubscribeAction, UnRegisterAction, MoveAction, ArriveAction, DepartAction, TravelAction, OrganizeAction, AllocateAction, AcceptAction, AssignAction, AuthorizeAction, RejectAction, ApplyAction, BookmarkAction, PlanAction, CancelAction, ReserveAction, ScheduleAction, PlayAction, ExerciseAction, PerformAction, SearchAction, SeekToAction, SolveMathAction, TradeAction, BuyAction, OrderAction, PayAction, PreOrderAction, QuoteAction, RentAction, SellAction, TipAction, TransferAction, BorrowAction, DonateAction, DownloadAction, GiveAction, LendAction, MoneyTransfer, ReceiveAction, ReturnAction, SendAction, TakeAction, UpdateAction, AddAction, InsertAction, AppendAction, PrependAction, DeleteAction, ReplaceAction
Website: https://schema.org/g/latest/
21 - JSON-LD
Introducing semantics into JSON so machines can understand meaning.
JSON-LD (JavaScript Object Notation for Linking Data) is a W3C standard for expressing linked data in JSON. It adds lightweight semantics to ordinary JSON so machines can understand what the data means, not just its shape—by mapping keys to globally unique identifiers (IRIs) via a @context. Common features include @id (identity), @type (class), and optional graph constructs (@graph).
Properties: base, containers, context, direction, graph, imports, included, language, lists, nests, prefixesm propagate, protected, reverse, set, types, values, versions, and vocabulary
Website: https://json-ld.org/
22 - Spectral
Enforcing style guides across JSON artifacts to govern schema.
Spectral is an open-source API linter for enforcing style guides and best practices across JSON Schema, OpenAPI, and AsyncAPI documents. It helps teams ensure consistency, quality, and adherence to organizational standards in API design and development.
While Spectral is a tool, its rules format is increasingly treated as a de facto standard. Spectral traces its roots to Speccy, an API linting engine created by Phil Sturgeon at WeWork. Phil later brought the concept to Stoplight, where Spectral and the next iteration of the rules format were developed; Stoplight was subsequently acquired by SmartBear.
With Spectral, you define rules and rulesets using properties such as given, then, description, message, severity, formats, recommended, and resolved. These can be applied to any JSON or YAML artifact, with primary adoption to date around OpenAPI and AsyncAPI.
The project’s GitHub repository hosts active issues and discussions, largely focused on the CLI. Development continues under SmartBear, including expanding how rules are applied across API operations and support for Arazzo workflow use cases.
Most commonly, Spectral is used to lint and govern OpenAPI and AsyncAPI specifications during design and development. It is expanding into Arazzo workflows and can be applied to any standardized JSON or YAML artifact validated with JSON Schema—making it a flexible foundation for governance across the API lifecycle.
License: Apache
Tags: Rules, Governance
Properties: rules, rulesets, given, then, description, message, severity, formats, recommended, and resolved properties
GitHub: https://github.com/stoplightio/spectral
Standards: JSON Schema
23 - Vacuum
Enforcing style guides across JSON artifacts to govern schema.
VACUUM rules in the context of API linting are configuration definitions that specify quality and style requirements for OpenAPI specifications. RuleSets serve as comprehensive style guides where each individual rule represents a specific requirement that the API specification must meet. These rules are configured using YAML or JSON and follow the Spectral Ruleset model, making them fully compatible with Spectral rulesets while adding vacuum-specific enhancements like an id property for backward compatibility and flexible naming. A RuleSet contains a collection of rules that define what to check, where to check it, and how violations should be handled, allowing organizations to enforce consistent API design standards across their specifications.
Each rule within a RuleSet consists of several key components: a given property that uses JSONPath expressions (supporting both RFC 9535 and JSON Path Plus) to target specific sections of the OpenAPI document, a severity level (such as error, warning, or info) that indicates the importance of the rule, and a then clause that specifies which built-in function to apply and what field to evaluate. For example, a rule might target all tag objects in an API specification using $.tags[*] as the JSONPath expression, then apply the truthy function to verify that each tag has a description field populated. Built-in core functions like casing, truthy, and pattern provide the logic for evaluating whether specifications comply with the defined rules, enabling automated validation of API documentation quality, consistency, and adherence to organizational or industry standards.
Vacuum is a soft fork of Spectral, keeping the base format for interoperability, while also taking the specification into a new direction to support OpenAPI Doctor and Vacuum linting rules functionality in tooling and pipelines.
License: Apache
Tags: Rules, Governance
Properties: rules, rulesets, given, then, description, message, severity, formats, recommended, and resolved properties
GitHub: https://quobix.com/vacuum/rulesets/understanding/
Standards: JSON Schema, Spectral
24 - Open Policy Agent (OPA)
Unifies policy enforcement for authentication, security, and auditability.
OPA (Open Policy Agent) is a general-purpose policy engine that unifies policy enforcement across your stack—improving developer velocity, security, and auditability. It provides a high-level, declarative language (Rego) for expressing policies across a wide range of use cases.
Originally developed at Styra in 2016, OPA was donated to the Cloud Native Computing Foundation (CNCF) in 2018 and graduated in 2021.
Rego includes rules and rulesets, unit tests, functions and built-ins, reserved keywords, conditionals, comprehensions/iterations, lookups, assignment, and comparison/equality operators—giving you a concise, expressive way to author and validate policy.
You can contribute on GitHub, follow updates via the blog and its RSS feed, and join conversations in the community Slack and on the OPA LinkedIn page.
OPA works across platforms and operational layers, standardizing policy for key infrastructure such as Kubernetes, API gateways, Docker, CI/CD, and more. It also helps normalize policy across diverse data and API integration patterns used in application and agent automation.
License: Apache
Tags: Policies, Authentication, Authorization
Properties: rules, language, tests, functions, reserved names, grammar, conditionals, iterations, lookups, assignment, equality
Website: https://www.openpolicyagent.org/
25 - CSV
Lighter weight data serialization format for data exchange.
CSV (Comma-Separated Values) is a simple, plain-text file format used to store tabular data in a structured way where each line represents a row and values within each row are separated by commas (or other delimiters like semicolons, tabs, or pipes). This straightforward format makes CSV one of the most universally supported data exchange formats, readable by spreadsheet applications like Microsoft Excel, Google Sheets, and LibreOffice Calc, as well as databases, data analysis tools, and virtually every programming language. CSV files are human-readable when opened in a text editor, showing data in a grid-like structure that closely mirrors how it would appear in a spreadsheet. The format’s simplicity—requiring no special markup, tags, or complex syntax—makes it ideal for representing datasets, lists, reports, and any tabular information where relationships between columns and rows need to be preserved.
Despite its simplicity, CSV has become essential for data import/export operations, data migration between systems, bulk data loading into databases, and sharing datasets for data analysis and machine learning. The format is particularly valuable in business contexts for handling customer lists, financial records, inventory data, sales reports, and scientific datasets. CSV files are compact and efficient, requiring minimal storage space compared to more verbose formats like XML or JSON, which makes them ideal for transferring large datasets over networks or storing historical data archives. However, CSV has limitations: it lacks standardized support for data types (everything is typically treated as text unless parsed), has no built-in schema definition, struggles with representing hierarchical or nested data, and can encounter issues with special characters, line breaks within fields, or commas in data values (typically addressed by enclosing fields in quotes). Despite these constraints, CSV remains the go-to format for flat, rectangular data exchange due to its universal compatibility, ease of use, and the fact that it can be created and edited with the most basic tools, from text editors to sophisticated data processing frameworks.
Tags: Data Format
Properties: Text-Based, Plain Text Format, Tabular Data, Row-Based Structure, Column-Based Structure, Delimiter-Separated, Comma Delimiter, Alternative Delimiters, Tab-Separated Values, Pipe-Separated, Semicolon-Separated, Human-Readable, Machine-Parsable, Flat File Format, Simple Syntax, Minimal Markup, No Tags, No Attributes, Lightweight, Compact, Small File Size, Efficient Storage, Fast Parsing, Universal Support, Cross-Platform, Language-Agnostic, Spreadsheet Compatible, Excel Compatible, Google Sheets Compatible, LibreOffice Compatible, Database Import/Export, SQL Bulk Loading, Data Exchange Format, Data Migration, Line-Based Records, Newline Row Separator, Field Delimiter, Quote Encapsulation, Double-Quote Escaping, Escape Characters, Header Row Support, Column Names, Schema-Less, No Data Types, Text-Only Values, No Type Enforcement, No Metadata, No Validation, No Comments, No Processing Instructions, RFC 4180, MIME Type text/csv, File Extension .csv, UTF-8 Encoding, ASCII Compatible, Character Encoding Support, Special Character Handling, Embedded Commas, Embedded Quotes, Embedded Newlines, Field Quoting, Optional Quoting, Whitespace Handling, Trailing Spaces, Leading Spaces, Empty Fields, Null Values, Missing Data Support, Sparse Data, Dense Data, Rectangular Grid, Fixed Columns, Variable Rows, No Nesting, No Hierarchy, No Relationships, Flat Structure, Single Table, No Joins, No Foreign Keys, Streaming Compatible, Incremental Processing, Line-by-Line Reading, Memory Efficient, Large File Support, Append-Only, Chronological Data, Time Series Data, Log Files, Sequential Access, Random Access, Indexing Support, Sorting Compatible, Filtering Compatible, Aggregation Compatible, Data Analysis, Statistical Analysis, Machine Learning Datasets, Training Data, Feature Vectors, Pandas Compatible, R Compatible, Python CSV Module, Java CSV Libraries, .NET CSV Support, Excel Formula Support, Cell Formatting Loss, No Styling, No Colors, No Fonts, No Borders, No Images, No Charts, Data-Only Format, Export Format, Import Format, Batch Processing, ETL Operations, Data Warehousing, Business Intelligence, Reporting Format, Audit Trails, Transaction Logs, Customer Lists, Contact Lists, Inventory Data, Sales Data, Financial Records, Scientific Data, Sensor Data, Measurement Data, Survey Results, Poll Data, Census Data, Demographic Data, Geographic Data, Coordinate Data, Latitude Longitude, Address Lists, Email Lists, Product Catalogs, Price Lists, Stock Data, Market Data, Historical Data, Archive Format, Backup Format, Version Control Friendly, Diff-Friendly, Merge-Friendly, Git Compatible, Text Editor Compatible, Command Line Tools, Awk Processing, Sed Processing, Grep Searching, Cut Command, Unix Tools, Shell Scripting, Automation Friendly, Cron Job Compatible, Scheduled Exports, API Responses, Web Scraping Output, Data Dumps, Bulk Downloads, FTP Transfer, Email Attachments, Cloud Storage, S3 Compatible, Azure Blob Storage, Google Cloud Storage, Database Export, MySQL Export, PostgreSQL Export, SQLite Export, Oracle Export, SQL Server Export, MongoDB Export, NoSQL Export, Data Conversion, Format Transformation, JSON to CSV, XML to CSV, Excel to CSV, CSV to JSON, Interoperability, Legacy System Support, Backwards Compatible, Universal Standard, Industry Standard, De Facto Standard, Widely Adopted, Mature Format, Production Ready, Battle Tested, Simple Implementation, Easy Generation, Easy Parsing, Minimal Dependencies, No External Libraries Required, Low Overhead, High Performance, Scalable, Concatenation Support, Split Support, Chunking Support, Partitioning Support, Compression Compatible, Gzip Compatible, Zip Compatible, Tar Compatible
Wikipedia: https://en.wikipedia.org/wiki/Comma-separated_values
26 - HTML
The standard markup language powering the Web.
HTML (HyperText Markup Language) is the foundational markup language of the World Wide Web, created by Tim Berners-Lee in 1991, that defines the structure and content of web pages through a system of elements enclosed in angle-bracket tags. HTML provides the semantic framework for organizing information on the web, using tags like
for headings,
for paragraphs, for hyperlinks, for images,