File Integrity Signature Checker
Verify that any file is authentic and uncorrupted at the header level with our free online File Integrity Signature Checker. Upload any file and instantly check if its magic bytes (the binary signature all real files possess) match its declared extension. The tool reads the first 128 bytes of your file, matches them against a database of 120+ known file signatures across 16 categories, and performs deep header structure validation for common formats like JPEG (marker/E0/E1 detection), PNG (IHDR chunk and dimension validation), PDF (version parsing), ZIP (local vs EOCD header), EXE (PE offset), and ELF (class/endian). Results include a clear integrity score (0-100), a detailed list of pass/fail/warning findings, extension match status, and the raw hex/ASCII dump of the header bytes for advanced analysis. All processing stays in your browser. Your files are never uploaded to any server.
File Integrity Signature Checker
Upload any file to verify its magic bytes match its extension and check for header-level corruption. A fast, lightweight integrity check for any file type.
Drop a file here or click to browse
Any file type - supports 120+ format signatures
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What is the File Integrity Signature Checker and how is it different from a regular file type detector?
The File Integrity Signature Checker goes beyond simple file type identification. While a regular detector only tells you what format a file appears to be, this tool also (1) verifies that the file extension matches the detected magic bytes, (2) performs deep header structure validation for common formats (checking for JPEG markers, PNG IHDR chunks, PDF version strings, PE headers, and more), and (3) calculates an overall integrity score. It's designed as a quick triage tool for file authenticity and header-level corruption detection.
How many file signatures are supported?
The tool detects 120+ known file signatures across 16 categories including Images (JPEG, PNG, GIF, WebP, BMP, TIFF, AVIF, HEIC, PSD, RAW formats), Audio (MP3, FLAC, OGG, WAV, AAC, AIFF, MIDI), Video (MP4, MKV, WebM, AVI, WMV, FLV, MOV), Documents (PDF, DOCX, XLSX, PPTX, ODF, RTF, EPUB), Archives (ZIP, RAR, 7z, TAR, GZIP, BZIP2, XZ, ZSTD), Executables (PE, ELF, Mach-O), Fonts, Certificates, and more.
What does the integrity score mean?
The integrity score ranges from 0 to 100 and is calculated based on the number and severity of findings. A score of 80-100 indicates the file header is valid, the extension matches, and no issues were found. A score of 50-79 indicates warnings were found (e.g., unknown extension, very small file size). A score below 50 indicates critical issues like extension mismatch, corrupted header bytes, or an undetectable file format. The score is a quick visual indicator of overall file health.
What does "extension mismatch" mean and why is it important?
An extension mismatch means the file's declared extension (e.g., ".pdf") does not match its detected magic bytes (e.g., the file actually starts with "MZ" indicating a Windows executable). This is a significant security concern because attackers often rename malicious files to appear harmless. For example, an executable named "invoice.pdf.exe" might display as "invoice.pdf" on systems that hide known extensions. Always investigate extension mismatches before opening the file.
Can this tool detect corrupted files?
Yes, within limits. The tool can detect header-level corruption by checking if the first bytes match expected magic byte patterns and verifying format-specific header structures where applicable. For example, it checks if PNG files have a valid IHDR chunk with non-zero dimensions, if PDF files contain a version string, and if executables have valid PE headers. However, corruption deeper in the file body (beyond the first 128 bytes) would not be detected by this tool.
What file types receive deep header structure validation?
The tool performs deep header validation for the most common file formats: JPEG (marker structure, JFIF/EXIF detection), PNG (IHDR chunk, dimension validation), GIF (version validation), PDF (version detection), ZIP (local header vs EOCD detection), EXE/PE (PE header offset validation), ELF (class and endian detection), and RIFF containers (AVI vs WAV identification). More formats are added regularly.
Can I use this tool to verify software downloads?
Yes, this tool provides a quick pre-check for downloaded software installers and executables. It can verify that the file has the correct magic bytes for its claimed format (e.g., .exe files start with "MZ", DMG files start with "Cr24..."). However, for security-critical verification, always use cryptographic hash verification (SHA-256) alongside this signature check. The integrity checker confirms the file type matches expectations, but a hash check confirms the file hasn't been modified at all.
Why does the tool only check the first 128 bytes?
File format signatures (magic bytes) are always located in the file header, typically within the first 4-64 bytes. Checking 128 bytes is more than sufficient to identify the file format, verify the header structure, and detect corruption at the start of the file. Checking beyond the header would require format-specific parsing of the entire file, which is beyond the scope of this quick integrity triage tool and would make it much slower, especially for large files.
Is my data safe and private?
Absolutely. All processing happens entirely in your browser using JavaScript. Your file is read into memory, analyzed for its magic bytes and header structure, and then discarded. Nothing is uploaded to any server, transmitted over the network, stored, or logged. You can verify this by inspecting the network tab in your browser's developer tools.