Most API governance tooling assumes a pipeline, an account, and a server that your document gets uploaded to. That is the wrong default for the most common moment of all: someone has a spec open and wants a fast, honest read on it. So we built API Validator — a browser-first governance tool that lints your document where it already is, with nothing leaving the page.
Try it → validator.apicommons.org
Four Artifact Types, On Purpose
API Validator lints OpenAPI (3.x and Swagger 2.0), AsyncAPI, Arazzo, and JSON Schema — and nothing else. The narrowness is deliberate: this is the tool you open to check one document, not a platform to adopt. Spectral runs entirely client-side, so your tokens and your specs never touch a backend.
A detail we care about: Swagger 2.0 is governed at full parity with OpenAPI 3.x. The curated OpenAPI catalog lints swagger: "2.0" documents exactly as it lints 3.x — rules are either broadened to match both structures or shipped as format-gated oas2/oas3 twins, so a rule only fires on the versions it applies to and never false-positives across formats. Most of the world’s OpenAPI is still 2.0; a validator that ignores that is ignoring the corpus.
Educate First, Enforce by Choice
Every rule ships at info. The default posture is to teach, not to block; you raise individual rules to warn or error for the conventions you decide to enforce, and those overrides persist in your browser. The rule editor is a focused form — severity, message, and description — with no raw-YAML foot-guns.
The catalog itself is best-of-breed, compiled from the first-party API Evangelist OpenAPI ruleset plus public, redistribution-compatible Spectral rulesets from SPS Commerce, Adidas, Trimble, Paystack, DigitalOcean, Microcks, and more — all Apache-2.0 or MIT, with attribution and vendored licenses recorded in the repo.
More Than a Linter
Search GitHub, GitLab, or Bitbucket with your own token and load any artifact straight into the Monaco editor with a YAML ⇄ JSON toggle. Render readable docs from the current artifact, run per-artifact utilities — bundle $refs, componentize, split by tag or channel or workflow, migrate JSON Schema drafts — and assemble everything you have saved into a single APIs.json 0.21 index you can download.
API Validator is one of the API Commons tools, and like the rest of them it is open, portable, and Spectral underneath — because the rules that decide whether an API is any good should not be locked inside a vendor. This is the first in a series introducing the tools one at a time.