# File type detector

> Compare a file’s reported type and header signature.

[Open tool](https://www.toolcabana.com/tw/file-type) · [Audio, video and files](https://www.toolcabana.com/tw/category/audio-video-and-files)

Tool ID: file-type. Requested language: tw. Description language: en. Complete guide translation: no; untranslated sections use English.

## Overview (en)

The file type detector compares the type your browser reports for a file with the signature found in its first bytes. It recognizes PNG, JPEG, GIF, WebP, PDF, WAV, MP3 with an ID3 tag, ZIP containers and the ISO media family that includes MP4, HEIF and AVIF. A table shows the filename, browser MIME type, detected signature, first 16 bytes in hex and file size.

## Supported tasks (en)

Compare a file’s reported type and header signature.

## Steps (en)

1. Choose a source file. If the tool accepts multiple files, arrange them in the order you want.
2. Check the source format before running the operation.
3. Run file type detector, review the output, then use the available copy or download controls.

## Settings

No additional settings.

## Limitations (en)

Media input is bounded to 50 MB per file and 100 MB combined. WebAssembly conversions have a 180-second limit and may require substantial browser memory.

## Example input

```text
A handy tool for every little task.
```

## Privacy and connections (en)

This operation processes its source in your browser. Copy and download are explicit actions; source input is not saved in an account or history.

## Questions (en)

### How can I tell if a file extension is wrong?

Compare the Browser MIME type row, which usually follows the extension, with the Header detection row, which comes from the file's actual bytes. If a file named .jpg shows a PNG signature, the extension does not match the content.

### Why does my DOCX or XLSX file show as a ZIP container?

DOCX, XLSX and EPUB files are ZIP archives internally and start with the same PK signature. The detector reports a ZIP container that may be one of these formats rather than naming the exact document type.

### Does the file type detector check whether a file is safe?

No. It only reads the first 64 bytes to match a known signature. The tool notes that signature detection is a hint, not proof that a file is safe or intact. Unlisted formats show that no supported signature was identified.

### Where is my input processed?

This operation processes its source in your browser. Copy and download are explicit actions; source input is not saved in an account or history.

### What are the input limits?

Media input is bounded to 50 MB per file and 100 MB combined. WebAssembly conversions have a 180-second limit and may require substantial browser memory.

## Related tools

- [ZIP extractor](https://www.toolcabana.com/tw/unzip)
- [Batch file renamer](https://www.toolcabana.com/tw/rename-files)
- [ZIP creator](https://www.toolcabana.com/tw/zip-maker)