# Upload error: File type not allowed / unsupported file type

**Code:** `file_type_not_allowed` · **Category:** API · **Seen on:** REST API

The upload was rejected because the file’s type — extension, MIME type or actual content — isn’t on the allowed list.

## Meaning

Upload endpoints check the extension, the declared Content-Type of the file part, and often the file’s real signature (magic bytes). A HEIC photo renamed .jpg, a PDF uploaded as application/octet-stream, or an SVG on an image-only endpoint all fail.

Laravel says “The file must be a file of type: jpg, png”, WordPress “Sorry, you are not allowed to upload this file type”, Multer-based APIs “Unsupported file type”. This is different from 415, which is about the request’s overall Content-Type.

## Common causes

- Format not supported (HEIC, WEBP, SVG, DOCX…)
- Wrong MIME type on the file part (application/octet-stream)
- Extension doesn’t match the real content
- Endpoint allow-list stricter than expected

## Quick fix

1. Convert to an allowed format (JPEG/PNG/PDF)
2. Set the correct MIME type on the file part
3. Check the endpoint’s allowed types in the docs

## Detailed fix by platform

### Node.js

1. 

```javascript
const form = new FormData();
form.append('file', new Blob([buf], { type: 'image/png' }), 'photo.png');
await fetch(url, { method: 'POST', body: form });   // let fetch set the multipart boundary
```


### curl

1. `curl -F 'file=@photo.png;type=image/png' https://api.example.com/v1/uploads`

## How to diagnose

1. **Real type** — file --mime-type photo.png
2. **Declared type** — Content-Type of the multipart part
3. **Allowed** — Endpoint allow-list

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Source: [WhatIsMyError](https://whatismyerror.com/errors/api/unsupported-file-type)