Playground

Paste two versions of a contract. Get the breaking changes, with rule ids.

No account, no upload, no server. This page loads CPython as WebAssembly and installs the same wheel a pip install would, so what runs is diff_services and evaluate_breaking — the functions the CLI calls, not a reimplementation of them.

Nothing leaves this tab

"Paste your API spec into our website" is a request most people should refuse, and most playgrounds are asking exactly that. This one cannot receive the text: the analysis happens in your browser, and there is no endpoint for it to be sent to.

The first run downloads Python and pydantic from jsDelivr, which takes a few seconds and tens of megabytes. It happens on the first Compare, not on page load.

Old contract

New contract

Compare Reset to the sample

What it runs, and what it leaves out

Everything on the analysis path: the loader, every breaking-change rule, and the security checks on the new contract. OpenAPI 3.0/3.1/3.2, Swagger 2.0, AsyncAPI, GraphQL SDL and MCP tool manifests are all recognised by content, so pasting a GraphQL schema works without changing anything.

What it leaves out is everything that needs the network or the filesystem — drift --base-url, test, replay, regression, the server. A browser tab cannot probe your staging environment, and a page that pretended to would be lying about where the answer came from.

Two dependencies the package declares are not installed here: httpx and flask. Nothing on this path imports them — every command that needs them imports them inside the function that uses them — and installing them would add a dozen wheels to a first load for code this page cannot reach. The cost is that a future import of something new fails at runtime rather than at install time, so the page catches that and names the missing module instead of showing a blank result.

Getting the same answers locally

curl -fsSL https://raw.githubusercontent.com/webdevsamran/api-verity-lab/main/install.sh | sh
apiverity breaking old.yaml new.yaml

The CLI has the rest of it: semver policy, consumer impact, suppressions, runtime drift, the CI gate. Installing lists every channel.