Free desktop app
Studio
A native macOS client where the OpenAPI spec is the organising primitive: requests generated from the spec, responses checked against it, and schemas you can browse rather than hunt for. Free, open source, and it works with no account at all.
Universal build for Apple silicon and Intel · macOS 11+ · signed and notarized by Apple · free and MIT licensed
The idea
Stop describing your API twice.
Most API clients ask you to rebuild, by hand, something you already have. You own a spec that says what the endpoints are, what the parameters mean, and what a valid response looks like — and then you maintain a collection that says the same thing, less precisely, and drifts the moment the API changes.
Studio starts from the spec instead. Requests are generated from it, responses are checked against it, and when the contract changes the client changes with it. There's nothing to re-record.
Body — generated from the schema
{
"customerId": "cus_4Qk28Rd",
"currency": "EUR",
"items": [{ "sku": "SKU-1042", "qty": 2 }]
} What's in it
A real client, not a spec viewer.
Requests built from the schema
Parameters typed by what the spec says they are — an enum becomes a select, a boolean a toggle. Bodies arrive pre-populated with real field names and format-aware values.
no collection to maintain Schemas are first-class
Operations and component schemas are two separate tabs, not one buried in the other. Merged allOf fields, what references what, and an interactive graph.
browse, don't hunt Responses checked against the contract
Validated against the schema declared for the status code actually returned — including fields the response contains that the spec doesn't declare, which is how drift usually shows up first.
including undeclared fields Conformance runs
Run a tag or the whole spec and get a verdict per operation. The assertions come from the spec, so nobody wrote them and they can't rot. Exportable as markdown for a PR.
read-only by default No CORS, ever
Requests execute in Rust rather than the webview, so there's no preflight and no browser origin. Point it at localhost, a host the spec never mentions, or your own API.
native HTTP Built for corporate networks
Per-host certificate trust with a private CA bundle, proxy support honouring HTTPS_PROXY and NO_PROXY, configurable timeouts, redirect chains reported, per-API cookie jars.
the things that decide it works Privacy
A client for internal APIs has no business talking to anyone else.
Studio makes no request you didn't ask for. No telemetry, no analytics, no crash reporting.
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The rendered reference never fetches
The renderer is handed the document text, never a URL. A spec whose description references a remote image will not load it — that request would tell whoever wrote the spec that you opened it.
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A content security policy enforces it
Not a promise about today's dependencies — a policy on the webview that holds regardless of what any bundled library decides to do in a future version.
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One secret store, not two
Auth values are never stored per API. They live in an environment where they can be marked secret, so a bearer token can't quietly become a second, worse secret store.
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Certificate trust is deliberate
Per-host, and there is no global "ignore TLS errors" switch — that's how a tool teaches people to stop reading warnings. Skipping verification for a host is shown at send time.
Free, open source, and it works with no account.
Opening a spec, browsing operations and schemas, firing requests, checking responses, managing environments and history — all of it works offline with no sign-in. Connecting a spec0 organisation adds your team's catalog and hosted mocks; signing out reverts to purely local and loses nothing.
Universal build for Apple silicon and Intel · macOS 11 or later · signed and notarized by Apple, so it opens without a Gatekeeper warning · MIT licensed
The platform
Part of the spec0 platform
MCP Layer
Live API context for every coding agent.
API Registry
One governed home for every internal API.
Mock Servers
A schema-accurate mock the moment you publish.
Governance & Quality
Catch breaking changes before they ship.
AI Workflows
Spec-aware automation across your APIs.