Free File Extension Checker
Received a file you do not recognize? NToolHub’s File Extension Checker identifies it instantly. Type any extension — or paste a full filename — and learn what the format is, which category it belongs to, and which programs open it. With 50+ formats covered, from documents to disk images, you will never guess blindly again.
How to Use the File Extension Checker
- Type a file extension (like .pdf) or a full filename.
- Click “Check Extension” to identify it.
- See what the file is, its category, and what opens it.
Features
A database of 50+ extensions across documents, images, audio, video, archives, code, fonts, and e-books; smart parsing that extracts the extension from full filenames and paths; case-insensitive matching; and graceful guidance for unknown formats.
Benefits & Use Cases
Knowing a file type before opening protects against malware disguised with misleading names. It also saves time — you will open the right app first instead of trial and error.
Tips
Be cautious with .exe, .msi, and script files from unknown senders — identifying them is step one, scanning them is step two. On Windows, enable file extension visibility to spot double extensions like invoice.pdf.exe.
Frequently Asked Questions
Can it identify a file from its full name?
Yes. Paste something like report.final.docx and the tool extracts the extension automatically.
What should I do with an unknown extension?
Treat it cautiously. Do not open it until you verify the source, and consider scanning it with antivirus software.
Why do some extensions have multiple meanings?
A few extensions are reused across formats. The tool shows the most common meaning for each.
Is this a virus scanner?
No. It identifies file types but does not analyze file contents. Use antivirus software for safety checks.
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