OpenAPI to TypeScript SDK online — entirely in your browser
You have an OpenAPI 3.x document and need a typed TypeScript client. Cloud generators force uploads; CLI pipelines need Node and CI. This page explains a third path: run @hey-api/openapi-ts in the browser and download a ZIP without sending the spec anywhere.
The problem
API teams ship OpenAPI (or Swagger) specs, but consumers still hand-write fetch wrappers. Drift between docs and code causes runtime bugs. You want OpenAPI → TypeScript SDK generation that is fast to try, private for internal specs, and typed enough for production clients.
Common mistakes
- Pasting internal OpenAPI into a random online generator that uploads the file to a server you do not control.
- Copy-pasting example clients from docs that ignore paths, parameters, and response schemas already defined in the spec.
- Assuming “Swagger UI in the browser” is the same as generating a reusable TypeScript SDK package.
- Implying the generator is the official hey-api product site — transformer is an independent, browser-hosted workflow that uses the open-source @hey-api/openapi-ts package.
The right approach
Treat the OpenAPI document as the source of truth and generate the client from it. For private or one-off specs, keep generation local:
- Paste or upload OpenAPI 3.x JSON/YAML in the browser tool (content stays on your machine).
- Choose an HTTP client runtime (Fetch, Axios, Ky, ofetch) and enum / date options.
- Generate with @hey-api/openapi-ts in dry-run / in-memory mode, then download the file tree as a ZIP.
- Review types and SDK helpers before committing them to your app monorepo.
How approaches differ
| Approach | Spec leaves device? | Best for |
|---|---|---|
| transformer (this site) | No — client-side only | Private specs, quick trials, no install |
| hey-api / openapi-ts CLI | Only if you run it on your CI machine | Repeatable repo pipelines |
| Hosted generators | Usually yes (upload) | Public demos when policy allows |
Checklist before you generate
- Spec is OpenAPI 3.x (JSON or YAML) and parses without critical errors.
- You know which HTTP client your app already uses (or default to Fetch).
- Internal base URLs and auth are not hard-coded secrets in the public sample you paste.
- You will treat generated output as code review material, not blind copy-paste.
- You need privacy: confirm the tool page states no backend upload (transformer does).
Generate your TypeScript SDK now
Open the free browser tool, paste your OpenAPI document, configure hey-api options, and download a ZIP — nothing is uploaded.
Open OpenAPI → SDK tooltransformer is not affiliated with or endorsed by the hey-api project. Generation uses the open-source @hey-api/openapi-ts package inside your browser; product capabilities are limited to what this site implements (client selection, plugins subset, ZIP download).