---
title: "Output"
description: "Configure @hey-api/openapi-ts."
url: "https://heyapi.dev/docs/openapi/typescript/configuration/output"
---

You must set the output so we know where to generate your files.

## Output

[Section titled “Output”](#output)

Output can be a path to the destination folder or an object containing the destination folder path and optional settings.

* path

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: 'src/client',
  };
  ```

* object

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      path: 'src/client',
      // ...other options
    },
  };
  ```

You can learn more about complex use cases in the [Advanced](https://heyapi.dev/openapi-ts/configuration#advanced) section.

## File

[Section titled “File”](#file)

Control how files are named and annotated in the generated output.

### File Name

[Section titled “File Name”](#file-name)

You can customize the naming and casing pattern for files using the `fileName` option.

* default

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      fileName: '{{name}}',
      path: 'src/client',
    },
  };
  ```

* snake\_case

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      fileName: {
        case: 'snake_case',
      },
      path: 'src/client',
    },
  };
  ```

By default, we append every file name with a `.gen` suffix to highlight it’s automatically generated. You can customize or disable this suffix using the `fileName.suffix` option.

* default

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      fileName: {
        suffix: '.gen',
      },
      path: 'src/client',
    },
  };
  ```

* disabled

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      fileName: {
        suffix: null,
      },
      path: 'src/client',
    },
  };
  ```

* custom

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      fileName: {
        suffix: '.generated',
      },
      path: 'src/client',
    },
  };
  ```

### File Header

[Section titled “File Header”](#file-header)

The generated output includes a notice in every file warning that any modifications will be lost when the files are regenerated. You can customize or disable this notice using the `header` option.

* example

  index.gen.ts

  ```js
  /* eslint-disable */
  // This file is auto-generated by @hey-api/openapi-ts


  /** ... */
  ```

* config

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      header: (ctx) => [
        '/* eslint-disable */',
        ...ctx.defaultValue,
      ],
      path: 'src/client',
    },
  };
  ```

## Module

[Section titled “Module”](#module)

Control how module specifiers are generated in the output.

### Module Extension

[Section titled “Module Extension”](#module-extension)

Set `module.extension` to define the file extension used in import specifiers. This is useful when targeting environments that require fully specified imports (e.g., Node ESM or certain bundlers).

* example

  index.gen.ts

  ```js
  import foo from './foo.js';
  import bar from './bar.js';
  ```

* config

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      module: {
        extension: '.js',
      },
      path: 'src/client',
    },
  };
  ```

### Module Path

[Section titled “Module Path”](#module-path)

Use `module.resolve` for full control over how module specifiers are generated. This lets you override specific modules or redirect them to custom locations (e.g., CDNs or internal aliases).

* example

  index.gen.ts

  ```js
  import * as z from 'https://esm.sh/zod';
  ```

* config

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      module: {
        resolve(path) {
          if (path === 'zod') {
            return 'https://esm.sh/zod';
          }
        },
      },
      path: 'src/client',
    },
  };
  ```

## Source

[Section titled “Source”](#source)

Source is a copy of the input specification used to generate your output. It can be used to power documentation tools or to persist a stable snapshot alongside your generated files.

Enabling the `source` option with `true` creates a `source.json` file in your output folder.

openapi-ts.config.ts

```js
export default {
  input: 'hey-api/backend', // sign up at app.heyapi.dev
  output: {
    path: 'src/client',
    source: true,
  },
};
```

You can customize the file name and location using `fileName` and `path`. For example, this configuration will create an `openapi.json` file inside `src/client/source` directory.

openapi-ts.config.ts

```js
export default {
  input: 'hey-api/backend', // sign up at app.heyapi.dev
  output: {
    path: 'src/client',
    source: {
      fileName: 'openapi',
      path: './source',
    },
  },
};
```

To use the source without writing it to disk, you can provide a `callback` function. This is useful for logging or integrating with external systems.

openapi-ts.config.ts

```js
export default {
  input: 'hey-api/backend', // sign up at app.heyapi.dev
  output: {
    path: 'src/client',
    source: {
      callback: (source) => console.log(source),
      path: null,
    },
  },
};
```

## Post Process

[Section titled “Post Process”](#post-process)

Post-processing allows you to run commands on the generated output folder after files are written. This is typically used to run formatters, linters, or other cleanup tools.

Commands are executed in order, and each command receives the output path via the `path` placeholder.

### Presets

[Section titled “Presets”](#presets)

You can use built-in presets for common tools:

* biome:check

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      path: 'src/client',
      postProcess: ['biome:check'],
    },
  };
  ```

* biome:format

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      path: 'src/client',
      postProcess: ['biome:format'],
    },
  };
  ```

* biome:lint

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      path: 'src/client',
      postProcess: ['biome:lint'],
    },
  };
  ```

* eslint

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      path: 'src/client',
      postProcess: ['eslint'],
    },
  };
  ```

* oxfmt

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      path: 'src/client',
      postProcess: ['oxfmt'],
    },
  };
  ```

* oxlint

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      path: 'src/client',
      postProcess: ['oxlint'],
    },
  };
  ```

* prettier

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      path: 'src/client',
      postProcess: ['prettier'],
    },
  };
  ```

### Custom

[Section titled “Custom”](#custom)

You can also provide custom post processors:

openapi-ts.config.ts

```js
export default {
  input: 'hey-api/backend', // sign up at app.heyapi.dev
  output: {
    path: 'src/client',
    postProcess: [
      {
        command: 'dprint',
        args: ['fmt', '{{path}}'],
      },
    ],
  },
};
```

You can skip processing by adding the output path to the tool’s ignore file (for example `.eslintignore` or `.prettierignore`).

## Name Conflicts

[Section titled “Name Conflicts”](#name-conflicts)

As your project grows, the chances of name conflicts increase. We use a simple conflict resolver that appends numeric suffixes to duplicate identifiers. If you prefer a different strategy, you can provide your own `nameConflictResolver` function.

* config

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      nameConflictResolver({ attempt, baseName }) {
        return attempt === 0 ? baseName : `${baseName}_N${attempt + 1}`;
      },
      path: 'src/client',
    },
  };
  ```

* example

  index.gen.ts

  ```ts
  export type ChatCompletion = string;


  export type ChatCompletion_N2 = number;
  ```

## TSConfig Path

[Section titled “TSConfig Path”](#tsconfig-path)

We use the [TSConfig file](https://www.typescriptlang.org/tsconfig/) to generate output matching your project’s settings. By default, we attempt to find a TSConfig file starting from the location of the `@hey-api/openapi-ts` configuration file and traversing up.

* default

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      path: 'src/client',
      tsConfigPath: undefined,
    },
  };
  ```

* custom

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      path: 'src/client',
      tsConfigPath: './config/tsconfig.custom.json',
    },
  };
  ```

* disabled

  openapi-ts.config.ts

  ```js
  export default {
    input: 'hey-api/backend', // sign up at app.heyapi.dev
    output: {
      path: 'src/client',
      tsConfigPath: null,
    },
  };
  ```

## Custom Files

[Section titled “Custom Files”](#custom-files)

By default, you can’t keep custom files in the `path` folder because it’s emptied on every run. If you’re sure you need to disable this behavior, set `clean` to `false`.

openapi-ts.config.ts

```js
export default {
  input: 'hey-api/backend', // sign up at app.heyapi.dev
  output: {
    clean: false,
    path: 'src/client',
  },
};
```

Caution

Setting `clean` to `false` may result in broken output. Ensure you typecheck your code.

## Examples

You can view live examples on [StackBlitz](https://stackblitz.com/orgs/github/hey-api/collections/openapi-ts-examples) or on [GitHub](https://github.com/hey-api/openapi-ts/tree/main/examples).