Send Multipart Form Data

Upload files and form fields using multipart/form-data encoding.

Code

Utilities

const formData = new FormData();
formData.append('username', 'john');
formData.append('email', '[email protected]');
formData.append('file', new Blob(['Hello World'], { type: 'text/plain' }), 'hello.txt');

const response = await fetch('https://httpbin.org/post', {
  method: 'POST',
  body: formData
});
await response.json();

Browser·fetch() may be limited by CORS

Notes

Don't set Content-Type header manually - browser sets it with correct boundary
Use new Blob() to create file-like data or pass actual File objects
httpbin.org echoes back the form fields and files received

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