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File Structure Validator

Upload any file to validate its internal structure - checks headers, markers, chunks, CRC checksums, embedded objects, and structural integrity for JPEG, PNG, PDF, ZIP, MP3, and MP4 formats. Get a detailed pass/fail report with an integrity score (0-100), field-level issue descriptions with byte offsets, severity ratings, actionable recovery recommendations, and a downloadable validation report. All processing runs locally in your browser - no uploads, no signup, completely free.

File Structure Validator

Upload any file to validate its internal structure - checks headers, markers, chunks, CRC checksums, embedded objects, and structural integrity for JPEG, PNG, PDF, ZIP, MP3, and MP4 formats. Get a detailed pass/fail report with an integrity score (0-100), field-level issue descriptions, and recovery recommendations.

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Supports JPEG, PNG, PDF, ZIP, MP3, MP4 - structure validation in your browser

Features

Format-Specific Validation

Validates internal structure for six major file formats: JPEG (SOI/SOF/SOS/EOI markers, color components, precision), PNG (8-byte signature, IHDR/IDAT/IEND chunks, CRC-32 checksums), PDF (%PDF header, xref tables, stream balance, %%EOF marker), ZIP (local file headers, central directory, EOCD), MP3 (ID3v2 frames, MPEG sync), and MP4 (ftyp brand, moov/mdat/moof boxes, trak tracks).

Field-Level Issue Detection

Each check reports individual issues with exact byte offset, severity level (error/warning/info), plain-English explanation, and actionable recovery recommendations. CRC-32 mismatches, missing required markers, truncated data, unbalanced streams, and non-standard fields are all identified with precision.

Integrity Scoring & Classification

Every file receives a 0-100 integrity score with a human-readable label - Excellent, Good, Fair, Poor, or Corrupted. The score is weighted by severity: each failed check subtracts 25 points, each warning subtracts 5 points. At-a-glance pass/fail/warning counts give you an immediate sense of file health.

Security Pattern Scanning

PDF validation includes detection of embedded JavaScript, Launch/URI actions, embedded files, and suspicious objects. ZIP validation checks for unusual compression methods and truncated entries. All analysis is performed locally in your browser - no file uploads, 100% private.

Use Cases

File Corruption Assessment

When a file won't open in your usual application, use the structure validator to determine exactly what's wrong - corrupted headers, truncated data, missing markers, or CRC mismatches. Know whether the file is recoverable before spending time on repairs.

Forensic File Analysis

In digital forensics investigations, validate the structural integrity of recovered files, check for evidence of tampering (missing markers, injection points), and document file condition with detailed structural reports suitable for evidence logs.

Data Recovery Verification

After running file recovery software, verify that recovered JPEG images have valid SOI/EOI markers and PNG files have correct CRC-32 checksums. The integrity score gives you a quick measure of recovery quality.

File Type Confirmation

When a file has an ambiguous or missing extension, validate its structure to confirm the format. The validator reads format-specific markers beyond just magic bytes - checking JPEG marker chains, PNG chunk structures, and ZIP central directories for definitive identification.

Image Quality Assurance

For photographers and designers, validate exported JPEG and PNG files to ensure proper structure before sending to clients or uploading to print services. Catch truncated files, missing color profiles, and broken metadata chunks before they cause problems.

Archive Integrity Checks

Validate ZIP archives for structural completeness - ensure local file headers match central directory entries, check for truncated entries, and verify the end-of-central-directory record. Essential before distributing software packages or transferring archives.

About

What Is File Structure Validation?

File structure validation goes beyond magic byte detection to verify that a file's internal organization matches its format specification. Each format (JPEG, PNG, PDF, ZIP, MP3, MP4) has a defined structure with specific markers, headers, chunks, and checksums. The validator parses these structures byte-by-byte, checking for required elements, correct ordering, proper field values, and data integrity through CRC or checksum verification.

JPEG & PNG Structural Analysis

JPEG validation checks the marker-based structure: SOI (Start of Image), SOF (Start of Frame with dimensions and color components), SOS (Start of Scan), and EOI (End of Image). Each APP marker is verified for correct length. PNG validation checks the 8-byte signature, required IHDR/IDAT/IEND chunk sequence, and computes CRC-32 checksums for every chunk to detect data corruption.

PDF & ZIP Structure Verification

PDF validation checks the %PDF header, cross-reference table, trailer dictionary, %%EOF marker, and stream balance. It also scans for security-relevant elements like embedded JavaScript and Launch actions. ZIP validation parses local file headers, compression methods, central directory entries, and the End of Central Directory record - detecting truncation and non-standard structures.

100% Private Browser-Based Processing

All file validation runs entirely in your browser using the File API and Uint8Array operations. Your files never leave your device - no uploads, no server requests, no third-party services. Only the first 64KB of each file is read for analysis. This makes the tool suitable for validating sensitive, confidential, or proprietary files including security research samples and personal documents.

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FAQ
What is a file structure validator?
A file structure validator reads and parses the internal organization of a file to verify it conforms to its format specification. Instead of just checking the first few magic bytes, it examines headers, markers, chunks, checksums, and structural elements throughout the file to detect corruption, truncation, tampering, and malformed data.
Which file formats does this tool support?
The tool validates six major file formats with deep structural analysis: JPEG (SOI/SOF/SOS/EOI markers, APP segments, color components), PNG (signature, chunk parsing with CRC-32), PDF (%PDF header, xref/trailer, stream balance, %%EOF), ZIP (local headers, central directory, EOCD), MP3 (ID3v2 tags, MPEG frame sync), and MP4 (ftyp box, moov/mdat/moof boxes, trak tracks).
How is the integrity score calculated?
The integrity score ranges from 0-100 and is calculated by subtracting weighted penalties from 100: each failed check subtracts 25 points, and each warning subtracts 5 points. The score is then classified as Excellent (90-100), Good (70-89), Fair (40-69), Poor (10-39), or Corrupted (0-9). A perfect score means all structural checks passed without any issues.
Does the file get uploaded to a server?
No. The File Structure Validator processes everything locally in your browser. Your files never leave your device - no server upload, no data logging, no third-party requests. Only the first 64KB of the file is read for analysis, making it suitable for sensitive and confidential files.
What is the difference between a fail and a warning?
A failed check indicates a critical structural problem - a missing required marker (like PNG IEND or JPEG EOI), a CRC-32 checksum mismatch, a truncated chunk, or an invalid field value. A warning indicates a non-critical anomaly - unusual but valid values, optional markers that are missing, or structural patterns that deviate from the norm but don't prevent the file from being usable.
Can this tool detect malware in files?
While not a dedicated antivirus scanner, the PDF validator can detect security-relevant elements: embedded JavaScript (commonly used in malicious PDFs), Launch/URI actions (which open external content), and embedded file attachments. ZIP validation can detect suspicious compression methods and non-standard structures. These indicators can help identify potentially dangerous files.
What does hex dump and ASCII dump mean?
The hex dump shows each byte as a two-digit hexadecimal value (00-FF), spaced for readability. The ASCII dump shows the same bytes as characters - printable characters appear as themselves, while non-printable bytes appear as dots. Together, they give you a complete picture of the file's beginning bytes for manual inspection.
Can a file pass structural validation but still be corrupted?
Yes, it's possible. The validator checks structural integrity, not content integrity. A file with valid headers, markers, and checksums could still have pixels that don't decode correctly (JPEG) or missing image data (PNG). However, passing all structural checks is a strong indicator that the file is well-formed and should open correctly in compatible software.
Is this File Structure Validator completely free to use?
Yes - 100% free, forever. No signup, no account, no premium tier, no usage limits, and no ads. Validate as many files as you need. All processing is done locally in your browser with zero server uploads.