What is APIs.io?
APIs.io is the search engine for the world’s APIs — a federated, open, and agent-friendly discovery network that helps people and machines find the right API for the job. Think of it as a public index of the API economy: for every provider on the network, APIs.io gathers up everything that describes how their APIs work — the APIs themselves, their specifications, data schemas, ready-to-run collections, workflows, governance rules, pricing and rate-limit profiles, and their AI agent surfaces — and organizes it into a single, consistent, searchable catalog.
What makes APIs.io different is that it is built to be read by machines as easily as by humans. Every provider is described using open specifications, starting with APIs.json as the root, so the entire catalog is structured, linkable, and machine-readable. That means it works equally well whether you are a developer browsing for a payments API, a search engine indexing the space, or an AI agent grounding itself in real, up-to-date API knowledge. Everything on the network is open-access and explicitly licensed for search indexing, AI grounding, RAG, and model training.
Today the network indexes 8,900+ API providers, 32,000+ APIs, 119,000+ JSON Schemas, 9,600+ API collections, and millions of individual data points across more than twenty distinct artifact types — all kept current from a Git-versioned catalog and rebuilt continuously.
The Specification Ecosystem
Every artifact in the network is described by one or more open specifications. APIs.json is the root — the meta-spec that ties everything else together — and every other spec is declared as a typed property inside a provider’s apis.yml file.
Live counts from the current build — APIs.json at the root, declaring every artifact type across the network. Updated automatically each week.
| Category | Specification | Role | Site |
|---|---|---|---|
| Discovery | APIs.json | Root meta-specification. Every provider is an apis.yml file that declares what specs it publishes and links to all of them. |
apis.io |
| Description | OpenAPI | REST/HTTP API descriptions — the largest catalog on the network | apis.apis.io |
| AsyncAPI | Event-driven, pub-sub, webhook, and streaming API descriptions | asyncapi.apis.io | |
| GraphQL | GraphQL endpoint descriptions, documentation, and reference links | graphql.apis.io | |
| Workflow | Arazzo | Multi-step API workflow specs — chains OpenAPI/AsyncAPI operations into sequences | arazzo.apis.io |
| Schema | JSON Schema | Data model schemas extracted from OpenAPI and AsyncAPI specs | schemas.apis.io |
| JSON-LD | Semantic context files that map API concepts to linked-data vocabularies | json-ld.apis.io | |
| Governance | Spectral Rules | API linting rulesets for validating OpenAPI and AsyncAPI descriptions | rules.apis.io |
| Collections | Open Collection | Open, vendor-neutral collection format (.opencollection.json) |
collections.apis.io |
| Postman Collection | Ready-to-run request collections in Postman format | collections.apis.io | |
| Operational | Plans | API pricing plan profiles (API Commons Plans format) | plans.apis.io |
| Rate Limits | Rate-limit policy profiles (API Commons Rate Limits format) | rate-limits.apis.io | |
| FinOps | Cost and billing profiles aligned with the FinOps Foundation FOCUS framework | finops.apis.io | |
| Agent | Claude Agent Skills | SKILL.md files published by providers — ready for direct AI agent use |
skills.apis.io |
| MCP (Model Context Protocol) | Official MCP server declarations — tools, auth, and connection details | mcp.apis.io |
How It Works
A central build pipeline reads from a set of provider repos at github.com/api-evangelist — Git-versioned APIs.json profiles, one per provider — and emits Jekyll collections into every subdomain site. Each site renders independently from its own collection via GitHub Pages.
Every provider and API page carries:
- A generated prose overview derived deterministically from structured frontmatter
- Schema.org JSON-LD (
Organization,WebAPI,Dataset,CollectionPage) - Open Graph and Twitter Card metadata
- A composite provider rating (0–100, banded Exemplar / Strong / Developing / Thin / Minimal) recomputed on every build
- Cross-page internal links to related providers, industries, regions, and specs
The network also publishes machine-readable feeds at every subdomain: llms.txt, sitemap.xml, and RFC 9727 api-catalog linksets. Start at apis.io/.well-known/api-catalog or apis.io/llms.txt.
Adding an API
Anyone can add an API at apis.io/add/. Paste your API or company URL and APIs.io reads your public well-knowns — APIs.json, an API Onboarding descriptor, OpenAPI, llms.txt, and MCP server — scores how discovery-ready you are, and lets you confirm the details before submitting. Don’t have a URL? Submit just a name and APIs.io researches your public API and agent-native surfaces and drafts the listing automatically. Accepted submissions are published as Git-versioned APIs.json profiles under github.com/api-evangelist and flow into the catalog on the next build.
Open Access
The APIs.io catalog is licensed for public use including search indexing, AI grounding and RAG, and model training. See apis.io/terms/ for the full terms.
Team & Support
APIs.io is a project led by Kin Lane (API Evangelist) and Steve Willmott (Timewarp Labs). It is built on APIs.json and API Commons, both maintained by Kin and Steve as open infrastructure for the next generation of API discovery.
The upstream provider catalog is maintained at github.com/api-evangelist and the network infrastructure lives at github.com/api-search.
Questions or issues: info@apievangelist.com or open an issue at github.com/api-search/network.