UseTool

File check: why won't my file open?

Find out what a file really is, whether it is incomplete, protected or uses a format your browser cannot read, and what helps.

Drop one file hereAny file type · nothing is uploaded

🔒 The file is examined on this device and never uploaded.

How it works

How it works

  1. 1

    Add what goes in

    Any single file, whatever its type or extension.

  2. 2

    Start it

    Nothing to set — it starts as soon as the file is there. Everything runs in this browser: no upload, no queue, no account.

  3. 3

    Take the result

    Read the findings and follow the suggested fix; nothing is saved or uploaded.

What this tool does

What goes in
Any single file, whatever its type or extension.
What comes out
You get a plain-language diagnosis with a traffic-light rating for each finding and the technical details.
What happens to quality
Your file is read, not changed. The original stays exactly as it was.
File check
Compares the signature in the first bytes with the extension, then checks the structure of the detected format: end markers, the ZIP directory, the MP4 index, PNG checksums, encryption flags and text encoding. Videos and images are also test-decoded in this browser.

When you need this

  • An invoice PDF from a customer portal shows an error in every viewer.
  • A video copied from a friend's phone plays on their device but not on your laptop.
  • A colleague's spreadsheet export arrives and nothing you try will open it.

Limits and notes

  • Which codecs work depends on your browser. Chrome and Edge read the most; Safari and Firefox refuse some.

Supported formats

Any file typenothing is uploaded

Good to know

Frequently asked questions

Can the file check repair a damaged file?

No. It explains what is wrong and points to the fix, for example downloading again, converting the format or asking for a password. Missing data cannot be restored.

How can it tell the real file type?

It reads the first bytes, which contain a signature for each format, and compares them with the extension. Structural checks then look for missing end markers, indexes and directories.

What files can I use here?

Any single file, whatever its type or extension.

What do I get back?

You get a plain-language diagnosis with a traffic-light rating for each finding and the technical details.

Does the file lose quality?

Your file is read, not changed. The original stays exactly as it was.

When does it not work?

Which codecs work depends on your browser. Chrome and Edge read the most; Safari and Firefox refuse some.

Does the original layout stay intact?

Text and CSV extraction does not reproduce the Office layout. Embedded pictures and media are copied byte for byte without re-encoding.

Why are only DOCX, XLSX and PPTX supported?

These modern Office files use the documented OOXML package format. Legacy DOC, XLS and PPT binaries and macro-enabled files are deliberately not processed.

Private by design

Your files stay on your device

The file is examined on this device and never uploaded.

Other tools

Ready-made

Workflows for this file type