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File Inspector

Drop a file to see what it really is: detected type, size, checksums, header bytes and warnings when the extension lies.

Processed locally in your browser

What is File Inspector?

A file name is only a label. This inspector reads the first bytes of the file and compares them with a table of more than 50 well-known signatures (PNG, JPEG, PDF, ZIP, Office documents, executables, audio, video, fonts, databases and more). For ZIP-based files it also looks at the inner entry names to tell DOCX, XLSX, PPTX, JAR, APK or EPUB apart.

For every file you get the size in human units and bytes, the type found by content and the MIME type implied by the extension, an extension mismatch warning, SHA-256, SHA-512 and MD5 computed in chunks (so large files work), the first 32 bytes in hex, a text-versus-binary verdict and an entropy estimate that hints at compressed or encrypted data.

How does it work?

  1. Drop one or several files on the drop zone (up to 1 GB each); they never leave your device.
  2. Read the report: detected type, MIME by extension and any mismatch warning.
  3. Copy the SHA-256 or MD5 to compare with a published checksum.
  4. Look at the first bytes and the entropy to judge whether the file is text, plain binary or compressed/encrypted.

Common use cases

  • Checking that a downloaded "PDF" or "invoice" really is a PDF and not an executable in disguise.
  • Finding out what an extension-less or oddly named file actually contains.
  • Getting SHA-256 and MD5 digests of a release file to verify against the vendor’s checksum.
  • Telling a .docx from a plain .zip or a .jar from a .apk before opening it.

Examples

Drop a file to see what it really is: detected type, size, checksums, header bytes and warnings when the extension lies.

Privacy

File Inspector runs entirely in your browser. The text or files you provide are processed on your device and are not uploaded, logged or stored on our servers.

Limitations

Detection is based on well-known signatures, so unusual or proprietary formats may show as unrecognised, and a matching type does not prove a file is safe: it is not a malware scanner. Entropy is estimated from the first 4 MiB.

Frequently asked questions

What are magic bytes?

Many formats start with a fixed byte pattern, for example PNG files begin with 89 50 4E 47 and PDFs with "%PDF". Reading these bytes reveals the real format regardless of the file name.

Why does it warn about an extension mismatch?

When the content is one format and the name suggests another (a JPEG named .png, or a program named .pdf), the file may be mislabelled or deliberately disguised. Check where it came from.

Is my file uploaded to compute the hashes?

No. Hashing runs in your browser, reading the file in chunks, so even multi-gigabyte files never leave your computer.

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