How does this tool detect file types?

It reads the first few bytes of the file (the file header) to find 'Magic Numbers' or signatures. These unique binary codes identify the format regardless of the file extension.

Is my file uploaded to a server?

No. All analysis happens locally in your browser using the HTML5 File API. Your data never leaves your device, ensuring 100% privacy.

Can it identify files with wrong extensions?

Yes! Because we check the binary signature, we can tell if a file named 'image.jpg' is actually a PDF or a PNG.

What are Magic Numbers?

Magic numbers are constant numerical or text values used to identify a file format. For example, JPEG files always start with 'FF D8 FF'.

Is there a file size limit?

Since processing is local, the limit depends on your browser's memory. We recommend files under 100MB for optimal performance.

Yes, iLikeTOOL's File Format Checker is completely free to use without any restrictions.

iLikeTOOL

File Analysis • 100% Client-Side

File Format Checker

Detect the real format, MIME type, and metadata of any file. Verify file integrity and identify unknown files securely using binary signatures.

Upload Any File to Check

Images, Documents, Media, Archives

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Reads binary headers (magic numbers) to detect the true format, ignoring extensions.

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100% Private

Analysis happens locally in your browser via HTML5 File API. Nothing is uploaded.

Why Check File Signatures?

File extensions can be misleading. A file named photo.jpg could actually be a malicious executable or a renamed PDF. iLikeTOOL's File Format Checker inspects the file's "Magic Numbers" (binary signature) to reveal its true identity. This is crucial for developers, security analysts, and anyone verifying file integrity.

Common Magic Numbers

Format	Hex Signature (Magic Number)
JPEG	FF D8 FF
PNG	89 50 4E 47 0D 0A 1A 0A
PDF	25 50 44 46 2D
ZIP	50 4B 03 04

Frequently Asked Questions

How does it detect the real format?

We read the first few bytes of the file (the "magic numbers"). For example, PNG files always start with the hex code 89 50 4E 47. This method works even if the file extension is wrong or missing.

Is my file uploaded to your server?

No. The analysis happens entirely within your web browser using the HTML5 File API. Your data remains private and secure on your device.

Can it check corrupted files?

It can verify if the file header is valid. If the header matches a known format but the file won't open, the internal data might be corrupted, but the format type is likely correct.

Is there a size limit?

Since processing is local, the limit is determined by your browser's memory. We recommend files under 100MB for the fastest performance.

Is this tool free?

Yes, iLikeTOOL's File Format Checker is 100% free for developers, designers, and everyone else.