Check a file by its actual header
This tool reads the first bytes of a file in your browser and estimates formats such as PDF, images, audio, video, archives, and ZIP-based containers. It can help identify extension mismatches.
Important note
This tool only estimates the file format. It cannot determine whether a file is safe or okay to handle. Avoid handling unknown files and verify them through trusted methods.
File format checker
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* Files are not uploaded. This tool reads only the first 4096 bytes in your browser.
FAQ
Q. Can this tool perform a security scan?
A. No. It only estimates the file format and cannot determine whether a file is safe.
Q. Is it risky if the extension and detected type differ?
A. It may indicate manual renaming or extension spoofing. Avoid handling files from unknown sources.
Q. Why are DOCX or XLSX files detected as ZIP?
A. Some Office documents use a ZIP-based container structure. APK, JAR, EPUB, and OpenDocument files may also be ZIP-based.
Q. Are files uploaded?
A. No. The tool reads only the first bytes inside your browser.