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Identify true file formats. Supports bulk uploads and determines file types using magic numbers instead of extensions.
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When file extensions are tampered with or missing, traditional methods fail to determine the true format. This tool accurately identifies the real file type by analyzing the magic number byte signatures at the beginning of the file. A magic number is a specific byte sequence at the start of a file used to identify its format, such as FF D8 FF for JPEG files. No matter how the file extension is modified, the tool returns the true MIME type (e.g., image/jpeg) and standard extension (e.g., .jpg).
How do you accurately identify file types?
By analyzing the magic number byte signatures in the file header. For example, PNG files always start with 89 50 4E 47.
What if the detection result doesn't match the extension?
Extensions can be manually modified, but file magic numbers cannot be forged. If a file with a .txt extension is detected as image/jpeg, it indicates a JPEG image disguised as text and should be renamed to .jpg.
We recommend a maximum size of 100MB per file and a limit of 50 files per bulk upload. Files are automatically destroyed after detection. Results are for reference only; encrypted or corrupted files may fail to be identified. Please do not upload executable files.
We recommend developers prioritize magic number validation over extensions when handling user-uploaded files. Typical scenario: When receiving "report.docx", the actual detection might show application/zip, indicating it is an archive disguised as a document. Common example: The magic number prefix for a PDF file is 25 50 44 46 (%PDF). A true PDF can be accurately identified even if it is renamed to "image.png".
