Standards From Practice

Some of the most widely implemented API contracts in the world were never ratified by anybody. S3, the OpenAI API, CKAN's Action API and Ethereum JSON-RPC became standards by being copied — and "compatible" stayed a marketing word until someone wrote down what it commits you to.

One of these is different. SCIM was ratified, in 2015, so describing it again would add nothing. Its profile carries the other axis instead: what the RFC says about each operation, quoted, beside what the industry actually built.

6 standards · published by API Commons

Models

The OpenAI Interface

211 providers in the API Evangelist catalog state OpenAI compatibility. 120 of them publish an OpenAPI harvested byte-identical from their own site, and those are the denominator. A provi...

338 graded 2 core 175 adopters 9 artifacts

Models

The Anthropic Messages Dialect

34 providers in the API Evangelist catalog state Anthropic compatibility. The cohort here is the 29 providers whose published OpenAPI declares at least one operation UNIQUE to the Anthrop...

244 graded 2 core 20 adopters 7 artifacts

Blockchain

The Ethereum JSON-RPC Interface

86 providers in the API Evangelist catalog claim EVM or Ethereum JSON-RPC compatibility. 42 declare an RPC-shaped endpoint and were probed; 21 returned usable results and are the denomina...

78 graded 22 core 40 adopters 10 artifacts

Open Data

The CKAN Action API

220 portals in the API Evangelist catalog run CKAN, across 210 distinct hosts. A version-spread sample was probed read-only; 36 produced usable results and are the denominator.

134 graded 63 core 48 adopters 9 artifacts

Storage

The S3 Interface

58 providers in the API Evangelist catalog claim S3 compatibility. 12 of them declare an S3 operation in a published OpenAPI. That is the denominator, and it is small — the weakest eviden...

116 graded 8 core 46 adopters 10 artifacts

Identity · ratified

SCIM 2.0

368 providers in the API Evangelist catalog mention SCIM — the largest claim cohort of any standard in this programme. 77 of them publish an OpenAPI containing a SCIM path, and those are ...

24 graded 5 core 320 adopters 9 artifacts

These are not designed APIs. Every profile here describes what the industry already implements, graded into core, extended and vendor tiers by measured adoption — from published specs where providers publish them, and by calling live endpoints where that is possible. Each standard was measured differently, each detail page says which method it used and why the others were unavailable, and every adopter entry carries the URL it was read from and the date it was read. A claim is recorded as a claim until something verifies it.

Formal standards

The ratified and published ones — specifications, industry standards, protocols, formats and security standards — read from the API Evangelist standards directory. Each has a page here, and each page lists the providers in the catalog whose own APIs.json carries the standard as a tag: the provider's statement that it is part of what they do, not a measurement by APIs.io. The six profiles above are where measurement exists.

441 standards · 189 carried by at least one provider in the catalog

Each standard lives in its own repository in the api-commons GitHub organization, with its profile, artifacts and adopter registry. The schema behind every registry is adopters.

Standards From Practice

The OpenAI Interface

The Anthropic Messages Dialect

The Ethereum JSON-RPC Interface

The CKAN Action API

The S3 Interface

SCIM 2.0

Formal standards

3D Graphics 2

AI 1

API Specification 1

Advertising 2

Automotive 1

Aviation 7

Compliance 1

Cross Domain 262

Crypto 1

Data Engineering 6

Education 7

Energy 5

Finance 15

Genomics 3

Geospatial 7

Government 3

HR 2

Healthcare 15

Identity 2

Insurance 6

IoT 12

Legal 2

Library 2

Life Sciences 3

Logistics 6

Manufacturing 2

Maritime 2

Media 1

Mobility 2

Mortgage 1

Payments 19

Procurement 2

Rail 1

Real Estate 4

Scholarly 5

Security 4

Social Services 1

Software Supply Chain 5

Space 1

Sustainability 3

Telecom 9

Trade 2

Transit 1

Travel 2