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Specification

A subject-matter collection covering API specifications, specification formats, specification-driven development, and the broader specification landscape. This includes OpenAPI, AsyncAPI, JSON Schema, GraphQL SDL, Arazzo, gRPC Protocol Buffers, RAML, API Blueprint, and other machine-readable API description formats. Specification-first development treats the API contract as the source of truth for code generation, documentation, testing, and governance.

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Providers working in Specification

Providers whose own tags share at least two of this topic's tags, most shared first — the top 30 of 56.

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Spotlight Rules Spotlight Rules is an openly-governed build of the Spectral API linter and, more importantly, the first attempt to publish the Spectral ruleset format as a standalone specification with its own portable JSON Schema — so that an organizatio… emerging 0
Postman Postman is the world's leading API platform, used by 35+ million developers to design, build, test, document, mock, monitor, and govern APIs across the entire API lifecycle. The platform spans Collections, Workspaces, the API Client, Spec… exemplar 21
Stoplight Stoplight is a collaborative, design-first API platform providing a visual editor for OpenAPI specifications, interactive hosted documentation, automatic mock servers, API style guides and governance, and open-source tools including Prism… exemplar 2
Spectral Spectral is an open-source API style guide enforcer and linter from Stoplight, providing a flexible JSON/YAML linting engine with built-in support for OpenAPI (v3.1, v3.0, v2.0), Arazzo v1.0, and AsyncAPI v2.x. Teams use Spectral to define… emerging 1
API Style Guides A landscape index of public API style guides published by leading technology companies and standards bodies. API style guides codify conventions for resource modeling, URI design, HTTP method use, status codes, error formats, pagination, v… emerging 11
SpecLynx SpecLynx provides enterprise-ready API tooling for authors and maintainers of OpenAPI, AsyncAPI, and Arazzo specifications. Built by veterans with 15+ years of Swagger and OpenAPI development experience, SpecLynx products prioritize securi… emerging 6
Bump.sh Bump.sh is "the modern API doc platform" — automatic, diff-aware documentation for OpenAPI and AsyncAPI specifications, plus a managed Model Context Protocol (MCP) platform that compiles Flower or Arazzo workflow documents into determinist… developing 1
Hey API Hey API builds open-source OpenAPI code generators and a hosted specification registry. @hey-api/openapi-ts turns an OpenAPI document into production-grade TypeScript — SDKs, types, Zod/Valibot/TypeBox validators, TanStack Query and SWR ho… developing 1
LAPIS LAPIS (Lightweight API Specification for Intelligent Systems) is a compact, LLM-native API description format authored by Daniel Garcia (cr0hn). It is designed as the format you convert your OpenAPI specifications to when the consumer is a… thin 1
Ogen Ogen is an Apache-2.0 OpenAPI v3 code generator for Go, maintained by the ogen-go organization. It reads an OpenAPI v3 document at build time and emits a statically typed Go client and server: code-generated JSON encoding with no reflectio… thin 1
Apicurio Apicurio is an open source API and schema tooling platform maintained by Red Hat under the Apache 2.0 license. It includes Apicurio Registry (a high-performance schema and API design registry), Apicurio Studio (a visual API designer for Op… thin 1
APIs.json APIs.json is an open, machine-readable specification that API providers can use to describe their API operations, similar to how websites use sitemap.xml. The format provides a lightweight means for individuals and organizations to documen… thin 1
Swagger Swagger is an open-source framework by SmartBear for designing, building, documenting, and consuming RESTful APIs using the OpenAPI Specification. Originally created by Wordnik in 2011, Swagger became the OpenAPI Specification (OAS) in 201… thin 5
APIGovernance.Dev APIGovernance.Dev is an AI-powered API governance platform that enforces API best practices through automated reviews trained on 10,000 public APIs. It provides the API Governance Top-10 list of best practices, automated CI/CD integration,… thin 1
Optic Optic is an MIT-licensed command-line tool for OpenAPI linting, diffing and testing. It compares two versions of an OpenAPI document with behaviour-aware diffing to catch breaking changes before they ship, enforces style-guide rulesets (br… emerging 1
Dredd Dredd is a language-agnostic, MIT-licensed open source command-line tool that validates a running HTTP API against its own API description document. It compiles every request/response pair documented in an API Blueprint, OpenAPI 2.0 or (ex… emerging 1
Jargon Jargon is a platform for Domain Driven Design for APIs and Enterprise Data Modelling. It provides text-based modelling, template-based API design, real-time validation, version control with breaking change detection, and generation of arti… emerging 1
APIs.io APIs.io is an open-source API search engine and federated discovery network built on the APIs.json specification. It indexes API providers and their individual APIs across the public internet along with the machine-readable artifacts they… exemplar 20
Routebase API lifecycle platform covering Design (visual OpenAPI editor), Mock (spec-driven mock servers), Test (suites, assertions, OWASP security scanning), Document (published docs portals), and Agents (MCP server), built around a single living O… strong 1
Netcracker Netcracker Technology is a Waltham, Massachusetts-based BSS/OSS and digital business software vendor and a wholly owned subsidiary of NEC Corporation. It sells cloud BSS, digital commerce and monetization, convergent charging, service and… strong 4
GSMA The GSMA (GSM Association) is the London-headquartered global trade body for the mobile industry, representing roughly 750 mobile network operators and around 400 companies in the wider mobile ecosystem, and the organiser of MWC Barcelona.… strong 18
ETSI ETSI, the European Telecommunications Standards Institute, is a not-for-profit standards development organisation headquartered in Sophia Antipolis, France, and one of only three bodies officially recognised by the European Union as a Euro… strong 24
SwaggerHub SwaggerHub is SmartBear's enterprise collaborative API design and documentation platform built around the OpenAPI specification. It provides tools for designing, building, documenting, and consuming RESTful APIs with support for OpenAPI 2.… developing 2
3GPP 3GPP (the 3rd Generation Partnership Project) is the global standards partnership that writes the technical specifications for mobile networks — GSM, UMTS, LTE, 5G and the ongoing 6G work — through seven regional Organizational Partners (A… developing 116
Elva API management platform for the agentic era: reads repos to build an API catalog, enforces per-audience contracts, generates tests, and turns APIs into governed, hosted MCP servers for AI agents. Built by Theneo. Exposes a public no-auth O… developing 1
AGNTCY AGNTCY is the open collective for agent interoperability, initiated by Outshift — Cisco's incubation group — and governed under the Linux Foundation (LF Projects, LLC), developed in the open across 52 public repositories. It publishes spec… developing 4
BTC War Live Market Data API Public, keyless, read-only real-time crypto market-data API from btcwar.net, exposing live Binance Spot snapshots and single-market observations for nine USDT pairs as JSON and Schema.org JSON-LD. Every response carries provenance, a sourc… developing 3
AsyncAPI AsyncAPI is a Linux Foundation project that improves the state of event-driven architectures by providing an open specification and tooling ecosystem for defining asynchronous and event-driven APIs. It enables developers to document, valid… developing 1
SmartBear SmartBear is a software company that provides AI-powered tools for API lifecycle management including design, testing, documentation, and governance. Their product portfolio includes SwaggerHub for API design and documentation, ReadyAPI fo… developing 1
OpenTravel Alliance The OpenTravel Alliance is a volunteer, non-profit travel technology standards body headquartered in Melbourne, Florida, United States. Since 1999 it has published the OpenTravel Specification — the OTA 1.0 XML message suite (releases 2001… developing 8

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API DesignAPI GovernanceAsyncAPIContract TestingJSON SchemaOpenAPISpecificationStandards