# File Type Detector (Magic Number) Identify a file by its magic-number byte signature, not the extension. Reads the uploaded file directly across ~70 types. > Canonical page: https://elysiatools.com/en/tools/file-type-detect - **Category:** Utilities - **Keywords:** file type, magic number, file signature, detect, identify, mime type, hex, binary, libmagic ## Overview Identify the **true type of a file by its magic-number byte signature** — not the (easily-spoofed) filename extension. Upload any file and the tool reads its leading bytes, then matches them against a database of ~70 magic-number signatures covering images, documents, audio, video, fonts, archives, executables and more. It reports the detected type, MIME type, recommended extension, and a **confidence score** reflecting how specific the match is. **How it differs from magic-number-detector** — that tool takes a *hex string you type by hand* and looks it up. This tool reads the **actual uploaded file** directly, supports offset-based signatures (e.g. ZIP-relative markers at byte 4), applies bitmasks (e.g. the RIFF-size field is ignored), and surfaces confidence + all candidates when multiple signatures match. **What it catches** - A .png that's actually a JPEG (mismatch warning). - An executable renamed .txt. - A WebP hidden inside a .jpg. - Office .docx / .xlsx (which are really ZIP containers). - Mach-O / ELF / PE executables, Java .class, SQLite databases, fonts, etc. **Confidence** - ≥90%: long, anchored signature (e.g. PNG's 8-byte sequence at offset 0) — near-certain. - 70-89%: solid match but shorter signature. - 45-69%: ambiguous (e.g. a single leading byte like '{' for JSON). - <45%: weak guess. The hex dump of the first 64 bytes is always shown so you can verify the signature by hand. ## Inputs - **File to inspect** (file): The file to identify. Only the first 512 bytes are read — large files are safe to upload. - **Also show hex dump of first 64 bytes** (checkbox): Display the raw hex dump so you can verify the signature manually. ## When to use - When you suspect a file extension has been altered, spoofed, or stripped entirely. - When troubleshooting corrupted files or upload errors where a system rejects a file due to a mismatched MIME type. - When verifying the true format of unknown binary files, executables, or archives before opening them. ## How it works - Upload the target file; the tool safely reads only the first 512 bytes to protect performance and privacy. - The tool compares the leading bytes and offset-based signatures against a database of ~70 magic-number signatures. - It calculates a confidence score based on signature length and specificity, displaying the detected MIME type and recommended extension. - Optionally, view the raw hex dump of the first 64 bytes to manually inspect the binary header. ## Use cases - Identifying the true format of a file that has lost its extension or has an incorrect extension. - Inspecting suspicious files or email attachments to verify if they are disguised executables. - Debugging application upload failures by checking if a file's internal MIME type matches the expected format. ## Frequently asked questions ### How does this tool determine the file type? It reads the file's initial bytes (magic numbers) and matches them against a database of known signatures, ignoring the file extension. ### Is it safe to upload large files? Yes, the tool only reads the first 512 bytes of the uploaded file, making the process fast and secure even for large files. ### What does the confidence score mean? A score of 90% or higher indicates a long, specific signature match (like PNG), while lower scores indicate shorter or more ambiguous signatures. ### Can it detect files that have been renamed? Yes, renaming a file's extension does not change its internal byte signature, which this tool reads to identify the true format. ### How does this differ from the magic number lookup tool? 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