Truncated File Detector
Upload any file to check if it has been truncated - that is, cut short before its expected end. When a file download is interrupted, an export fails, or a transfer is corrupted, the file may be incomplete. Our Truncated File Detector reads the file's header to identify the format, then compares the actual file content against the expected end-of-file markers: JPEG EOI (FF D9), PNG IEND, GIF trailer (0x3B), PDF %%EOF, ZIP End of Central Directory, and BMP header-declared size. We also estimate how much data may be missing based on image dimensions or header-declared sizes. Clear results show whether your file appears complete, truncated, or unknown - with confidence ratings and hex dumps for verification. All processing is entirely local in your browser with nothing uploaded to any server. Free to use, no signup required.
Upload any file to check if it has been truncated (cut short). Our tool reads the file header and compares the expected end-of-file markers and size with the actual file - detecting incomplete downloads, failed exports, and corrupted transfers for JPEG, PNG, GIF, BMP, PDF, ZIP, GZIP, and more. All processing is local in your browser - no uploads, no signup required.
Drop a file here or click to browse
Any file type - max 200 MB. Detects truncation in JPEG, PNG, GIF, BMP, PDF, ZIP, GZIP, and more.
Our Truncated File Detector identifies file truncation by reading the file's header to determine the format, then checking for the expected end-of-file markers. For JPEG files, it looks for the EOI marker (FF D9). For PNG, it checks for the IEND chunk. For PDF, it searches for %%EOF. For BMP, it reads the file size from the header and compares it to the actual size. If the expected markers are missing or the file is smaller than expected, the file is flagged as potentially truncated. All analysis happens entirely in your browser - nothing is uploaded.
Why Use Our Truncated File Detector?
Multi-Format Truncation Detection
Detect truncated files across major formats: JPEG, PNG, GIF, BMP, PDF, ZIP, GZIP, and more. Our truncated file detector checks for expected end-of-file markers like JPEG EOI (FF D9), PNG IEND, PDF %%EOF, and ZIP EOCD - identifying incomplete transfers and corrupted files instantly.
Size-Based Validation
For formats like BMP that declare their size in the header, our truncated file detector compares the expected size against the actual file, calculating exactly how many bytes are missing. This provides precise evidence of truncation.
Truncated File Detector Online - No Installation
Use our truncated file detector directly in any browser with no downloads, plugins, or app installs required. All file analysis happens locally on your device - no uploads, no server processing. Check files from anywhere.
100% Free Forever
Our truncated file detector is completely free with no signup, no ads, and no usage limits. Check as many files as you need, up to 200 MB each - completely free, forever. All processing happens locally in your browser.
Common Use Cases for Truncated File Detector
Incomplete Download Detection
Use our truncated file detector to check if downloaded files were fully transferred. Files that fail mid-download often lack the proper end-of-file markers - our tool catches these incomplete transfers instantly.
File Transfer Verification
After transferring files via SCP, FTP, or cloud storage, verify integrity with our truncated file detector. A quick check can reveal whether the file arrived complete or was truncated during transfer.
Digital Forensics & Investigation
In forensic investigations, truncated files can indicate tampering, intentional data hiding, or system crashes. Our truncated file detector helps investigators quickly identify files that may have been altered.
Export & Render Validation
Verify that exported files from image editors, document creators, and conversion tools are complete. Our truncated file detector catches failed exports that appear to have the right size but are missing critical end markers.
Backup Integrity Checking
Periodically check backup archives for truncation. Our truncated file detector can scan ZIP and GZIP backup files to ensure they are complete and not corrupted due to storage errors.
Learning & Education
Understand file format structure by seeing what happens when files are truncated. Our truncated file detector demonstrates how each format uses specific end markers and why they are essential for file integrity.
Understanding File Truncation Detection
What is File Truncation?
File truncation occurs when a file is cut short - either partially transferred, corrupted during save, or deliberately truncated. A truncated file has all its header information intact (which is written first), but is missing its end-of-file markers and potentially a significant portion of its data. This makes truncation difficult to detect by casual inspection - the file appears to have a valid format from the header, but the content is incomplete. Our truncated file detector reads the file header to identify the format, then checks the tail bytes for the expected end markers and compares declared sizes with the actual file size.
How to Use This Truncated File Detector
- 1. Upload a file: Click the upload area or drag and drop any file (up to 200 MB). All analysis happens locally in your browser - your file never leaves your device.
- 2. Review the results: Our truncated file detector shows the detected format, whether the expected end-of-file marker was found, any missing byte count, and the hex dumps of the header and tail bytes for verification.
- 3. Take action: If the file is flagged as truncated, re-download or re-transfer the file from the source. For important files, consider using additional integrity checks like SHA-256 hash verification against the known good checksum.
Format-Specific Detection Methods
- JPEG: Checks for the End of Image marker (FF D9). Also scans for SOF markers to determine image dimensions and estimate expected file size for comparison.
- PNG: Checks for the IEND chunk at the end of the file. Parses the IHDR chunk for width, height, and bit depth to estimate the expected uncompressed data size.
- GIF: Checks for the trailer byte (0x3B). Every valid GIF must end with this byte.
- BMP: Reads the file size from the BMP header (bytes 2-5) and compares it directly to the actual file size - providing exact byte-level truncation measurement.
- PDF: Searches the tail bytes for the %%EOF end-of-file marker. Missing %%EOF is the most common indicator of a truncated or corrupted PDF.
- ZIP: Checks for the End of Central Directory record (PK\x05\x06) which must be present in every valid ZIP archive.
Limitations & Considerations
Our truncated file detector has some limitations. Files must be fully read into browser memory for analysis (up to 200 MB). Some formats (like plain text, JSON, or XML) don't have fixed end markers - the tool will report these as unknown. Encrypted or password-protected files cannot be scanned. The estimated missing byte count for JPEG and PNG is approximate and based on image dimensions. For definitive integrity verification, cryptographic hashes (SHA-256) or checksum files should be used alongside this tool. All analysis is performed entirely in your browser - no data is uploaded to any server.
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Frequently Asked Questions About Truncated File Detector
A truncated file is a file that has been cut short - it has a proper beginning (header) but is missing its ending (trailer) and potentially a significant portion of its data. This typically happens due to incomplete downloads, failed file transfers, disk errors, or program crashes during save. Truncated files often appear to have the correct format when you check the extension, but lack the complete data structure.
The truncated file detector supports JPEG, PNG, GIF, BMP, PDF, ZIP, GZIP, and WebP. For each format, it checks the expected end-of-file markers and compares declared sizes with actual sizes where available.
The tool reads the file header to identify the format using magic bytes (file signatures). It then checks the tail bytes for the expected end-of-file marker specific to that format - JPEG EOI (FF D9), PNG IEND, GIF trailer (0x3B), PDF %%EOF, or ZIP EOCD (PK 05 06). For formats like BMP that declare their size in the header, it compares the expected size against the actual file size.
Partial data recovery from truncated files may be possible depending on the format and extent of truncation. Image files often display partially even when truncated (the visible portion is valid). PDF recovery tools may be able to extract content before the point of truncation. However, our truncated file detector only detects truncation - it does not repair or recover files. For recovery, use format-specific repair tools.
A truncated file is specifically cut short - it has a valid header but is missing its end. A corrupted file may have its full length but contain incorrect or damaged data within. Our truncated file detector focuses on truncation. For broader corruption detection, use the File Structure Validator or File Integrity Signature Checker tools.
Re-download or re-transfer the file from its original source. If the file was created locally, check if the export or save process completed successfully. For important files, compare the truncated version against a known good copy using SHA-256 hash verification.
Absolutely. The truncated file detector processes everything entirely in your browser using the Web File API. Your file is read directly from your device and never uploaded to any server. The analysis results are generated locally and do not leave your computer.
The truncated file detector supports files up to 200 MB. This limit exists because the entire file must be read into browser memory for header and trailer analysis. For most use cases, this is more than sufficient.
Yes! Our truncated file detector is 100% free with no signup, no ads, and no usage limits. Check as many files as you need, up to 200 MB each - completely free, forever. All computation happens locally in your browser with no server interaction.