@metaengine/openapi-fetch

Generate TypeScript services and models from OpenAPI specifications using the native Fetch API.

Framework-agnostic — runs on Node, browsers, Vite, SvelteKit, Next.js, and any TS runtime that ships fetch.

Install

npm install --save-dev @metaengine/openapi-fetch

Or use directly with npx:

npx @metaengine/openapi-fetch <input> <output>

Requirements

• Node.js 18.0 or later
• .NET 8.0 or later runtime (Download)

Quick start

npx @metaengine/openapi-fetch api.yaml ./src/api \
  --documentation \
  --result-pattern

Production setup

npx @metaengine/openapi-fetch api.yaml ./src/api \
  --bearer-auth API_TOKEN \
  --timeout 30 \
  --retries 3 \
  --custom-header X-Tenant-ID=TENANT_ID \
  --error-handling

CLI options

| Option | Description | Default | |--------|-------------|---------| | --include-tags <tags> | Filter by OpenAPI tags (comma-separated, case-insensitive) | - | | --base-url-env <name> | Environment variable name for base URL (e.g. VITE_API_URL, NEXT_PUBLIC_API_URL) | API_BASE_URL | | --service-suffix <suffix> | Service naming suffix | Api | | --options-threshold <n> | Parameter count for options object | 4 | | --documentation | Generate JSDoc comments | false | | --import-meta-env | Use import.meta.env for env access (Vite, SvelteKit) | false | | --result-pattern | Return ApiResult<T> instead of T for structured error handling | false | | --middleware | Emit middleware hooks (onRequest, onResponse, onError) in client | false | | --error-handling | Smart error handling based on HTTP status semantics | false | | --bearer-auth <env-var-name> | Bearer token from env var (adds Authorization: Bearer <token>) | - | | --timeout <seconds> | Request timeout in seconds for all operations | - | | --retries <max-attempts> | Enable retries with exponential backoff (status codes 429, 503) | - | | --custom-header <header=envVarName> | Static header from env var. Repeatable. | - | | --strict-validation | Strict OpenAPI validation | false | | --date-transformation | Convert date strings in responses to Date objects | false | | --clean | Clean output directory (remove files not in generation) | false | | --verbose | Enable verbose logging | false | | --type-mapping <slug=target> | Override TS type for an OpenAPI format. Repeatable. See Type mapping overrides | - | | --help, -h | Show help message | - |

Type mapping overrides

Use --type-mapping to override the TS type emitted for a given OpenAPI (type, format) pair. Repeatable. Unknown slugs and unknown targets are hard errors.

| Slug | OpenAPI (type, format) | Default | --type-mapping value | |------|--------------------------|---------|------------------------| | int64 | (integer, int64) | number | int64=bigint | | decimal | (number, decimal) | number | decimal=string | | date-time | (string, date-time) | Date | date-time=string | | date | (string, date) | Date | date=string |

npx @metaengine/openapi-fetch api.yaml ./src/api \
  --type-mapping int64=bigint \
  --type-mapping date-time=string

See it live

Try the generator with your own spec at https://www.metaengine.eu/converters.

License

MIT

Support

For issues and feature requests, please visit: https://github.com/meta-engine/openapi-fetch/issues