Identify any file by its magic bytes, not the extension
- Upload any file — only the first few bytes are read, entirely in your browser
- See the true file format, MIME type, and which applications can open it
- Get warnings if the extension does not match the actual content
Proof: Magic bytes are embedded in the file itself and cannot be faked by renaming the extension
Find out what type of file you have by reading its magic bytes (file signature), not the extension. Detects mismatches between extension and actual content.
- Reads the first few bytes of any file to match against 40+ known file signatures (PNG, PDF, ZIP, MP4, EXE, and more).
- Shows the MIME type, expected extension, compatible applications, and a safety rating for every identified format.
- Flags extension mismatches that could indicate renamed files, corrupted downloads, or suspicious executables disguised as documents.
100% browser-side. Your file never leaves your machine.
File extensions can be changed by anyone. The only reliable way to know what a file actually contains is to read its magic bytes—a signature embedded in the first few bytes of every file. This tool does exactly that, instantly and privately.
Free, no signup, and 100% browser-side. Works with any file type.
File type identifier
Drop any file below to identify its true format by reading magic bytes.
Drop any file here or click to browse
Any file type — processed entirely in your browser
Your files never leave your browser.
Only the first few hundred bytes are read to identify the file signature. No data is sent to any server.
Why identifying file types matters
File extensions are just labels—they can be changed without altering the actual content. Relying on extensions alone creates real risks for security, compatibility, and data recovery.
Security
Attackers rename executables with harmless extensions like .pdf or .jpg. Checking magic bytes reveals the true format before you open anything from an untrusted source.
Compatibility
A file that will not open might simply have the wrong extension. Identifying the real format tells you which application to use and whether a simple rename fixes the problem.
Data recovery
Recovered files from damaged drives or backups often lose their extensions. Magic byte identification lets you restore the correct extension and open the file normally.
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Frequently asked questions
What are magic bytes in a file?
Magic bytes (also called file signatures) are specific byte sequences at the beginning of a file that identify its format. For example, PDF files always start with %PDF (hex 25 50 44 46), and PNG images start with 89 50 4E 47. These bytes are embedded in the file content and cannot be changed by renaming the extension.
Why does the file extension not match the detected type?
An extension mismatch means the file was renamed with a different extension than its actual format. This can happen when a download was saved incorrectly, someone renamed the file manually, or—in worst cases—when a malicious executable is disguised as a harmless document. Always verify the actual type before opening files from untrusted sources.
Is my file uploaded to a server?
No. This tool reads only the first few hundred bytes of your file directly in the browser using JavaScript. Your file never leaves your device—no data is sent to any server, stored, or logged.
What file types can this tool identify?
Over 40 common formats: images (PNG, JPEG, GIF, WebP, HEIC, AVIF, TIFF, BMP, PSD, SVG, ICO), documents (PDF, DOCX, XLSX, PPTX), audio (MP3, WAV, FLAC, OGG), video (MP4, WebM), archives (ZIP, RAR, 7Z, GZIP, TAR), fonts (WOFF, WOFF2, TTF, OTF), executables (EXE, ELF, Mach-O), and databases (SQLite).
How is file safety determined?
Files are rated based on their type, not a malware scan. Images, documents, and fonts are rated Safe. Archives (ZIP, RAR) are rated Caution because they can contain any file type inside. Executables (EXE, ELF) are rated Warning because they can run code on your system. For actual malware detection, use a dedicated antivirus tool.
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