Input
Preparing your workspace…
How to use
- Choose a file or drag it into the workspace.
- Read the automatically generated properties and leading Hex bytes.
- Copy the report or download file-info.json.
File properties and signature bytes
A filename extension and a browser MIME label are useful clues, but they do not always identify the underlying format. Leading signature bytes provide another clue to compare with those labels.
This inspector reads only the first 256 bytes of files within its 1 GiB limit. It reports basic properties rather than extracting the full contents or running the file.
Comparing the file clues
The filename, size, MIME label and modification time come from the selected browser File object. They are displayed separately from signature detection.
A recognized header can suggest formats such as PNG, PDF or ZIP. Containers can share signatures, so the same leading bytes may cover several more specific formats.
PNG signature bytes89 50 4e 47 0d 0a 1a 0a → PNGThe eight-byte PNG signature as a format hint, not a complete file-validation result.
What is not inspected
A short header is not full-file validation. It does not prove that the rest of the file is well formed, safe or from a trusted source.
This tool does not scan for malware, extract embedded documents or calculate a checksum of the entire file. Use File Checksum when you need a digest of all file bytes.
Using the report
Copy and Download export the report as JSON, including properties and the leading Hex bytes. They do not export the original file or upload it to DevToolsy.
Still PNG, JPEG and WebP: 20 MiB, 24 megapixels and 8,192 pixels per side. Base64: 2 MiB. SVG: 1 MiB. File inspection: 1 GiB with only the first 256 bytes read. Browser codec support varies. No files are uploaded.
Frequently asked questions
Does a recognized signature prove the file is safe?
No. Signature matching is a format hint, not malware scanning, integrity verification or proof of origin.
Why do the extension and detected type disagree?
Extensions can be renamed and MIME labels may be inferred by the browser. Compare the signature with a format-aware validator when you need a firmer answer.
Why is the detected signature unknown?
The file may use a format outside this tool’s signature list, have an incomplete header, or contain unrecognized data. Unknown is not a verdict on safety.
Does inspection read my whole file?
No. Only the first 256 bytes are read for the report, although file selection exposes basic properties such as name and size.
Do I need to press Generate after choosing a file?
No. Inspection starts automatically when a file is selected. Choose another file to inspect it, or use Clear to remove the current report.