AnyTool
Your files never leave your device. All processing happens locally in your browser.

How to view a file's internal structure and headers online?

Drop a file into AnyTool's File Anatomy Viewer and it auto-detects the format by magic bytes, then walks a hand-written parser into a labeled tree of sections and fields synced to a hex/ASCII pane. It validates PNG CRC-32 and shows entropy, 100% in your browser with no upload.

  • Auto-detects PNG, JPEG, GIF, BMP, WebP, WAV, ZIP, GZIP, PDF, ELF and PE by magic bytes
  • Expandable section/field tree synced to a virtualized hex view both ways
  • PNG CRC-32 validation, Shannon entropy and a byte histogram off the main thread
  • Export the parse tree as JSON or copy a field as a hex/C/Python/Go/Rust array
  • 100% in your browser - no upload, no signup, works offline

What is

File Anatomy Viewer

A File Anatomy Viewer is a tool that detects a binary file's format and dissects its internal structure - headers, sections, chunks and fields - showing each one's offset, length and decoded value beside the raw hex bytes.

Developer Tools

Related terms

Magic BytesHex ViewerFile Format ParserCRC-32 Validation

Frequently Asked Questions

Yes. The file is read locally with the File API and never uploaded - no server, no CDN, and it works offline.

Every byte stays on your device. AnyTool reads the file with File.arrayBuffer in your browser, parses it client-side, and runs entropy and CRC checks in a Web Worker. Nothing is sent to a server, there is no signup, and the tool works offline after the first load.

PNG, JPEG, GIF, BMP, WebP, WAV, ZIP, GZIP, PDF, ELF and PE, auto-detected by their magic bytes.

The viewer ships hand-written parsers for common formats - PNG, JPEG, GIF, BMP, WebP, WAV, ZIP, GZIP, PDF, ELF and PE - and detects the right one from the file's magic bytes. Each gets an expandable tree of sections and fields with offset, length, a decoded value and a plain-English note.

No. Cross-origin URL fetching is blocked by browser CORS, so you load files by drag-and-drop, file picker, or pasting hex or base64.

To honor the no-backend promise the tool never fetches remote files, and browsers block cross-origin reads anyway. Instead you drag-and-drop a file, pick one, or paste raw bytes as hex (like 89 50 4E 47) or a base64 string, and it parses instantly on the client.

Click the field in the structure tree and the hex pane scrolls to and highlights its exact byte range; click a byte to jump back to its field.

The tree and hex view are synced both ways. Selecting a node scrolls the virtualized hex/ASCII pane to its offset and highlights the range, and clicking any byte selects its owning field and expands the path to it in the tree. You can then copy just those bytes as a hex, C, Python, Go or Rust array.

Detailed Explanation

Technical Details

Format-Aware Structure Tree with Hex Sync

AnyTool File Anatomy Viewer detects a file's format from its magic bytes, then walks a compact hand-written parser into an expandable tree of sections and fields. Each node carries its byte offset, length, a decoded value and a plain-English note. Clicking a node scrolls a virtualized hex and ASCII pane to its exact byte range, and clicking a byte selects its owning field, giving Kaitai-style two-way navigation without a format spec to author.

  • Supports PNG, JPEG, GIF, BMP, WebP, WAV, ZIP, GZIP, PDF, ELF and PE
  • Bidirectional tree-to-hex and hex-to-tree selection
  • Hex grid is row-virtualized so multi-MB files stay responsive
  • Each field shows offset, length, decoded value and a spec note
Methodology

Per-Field Validation and Entropy Analysis

Beyond labeling, the viewer validates structure: it recomputes PNG CRC-32 checksums and flags magic-byte and spec violations with a colored verdict per node. It also computes full-file Shannon entropy and a 256-bin byte histogram, classifying data as low, structured, mixed or likely compressed or encrypted. The CRC and entropy work runs in a Web Worker so the hex and tree UI never blocks.

  • PNG CRC-32 recomputed and compared against the stored value
  • Shannon entropy reported as bits per byte from 0 to 8
  • Byte-distribution histogram over the whole file
  • Heavy CRC and entropy work runs off the main thread
Privacy & Security

Privacy and Honest Client-Side Limits

File anatomy is pure parsing, so the tool runs 100% client-side - the file is read with the File API, never uploaded, with no server or runtime CDN, and it works offline after first load. The trade-offs are deliberate: it does not fetch files from a URL because browser CORS blocks cross-origin reads and a proxy would break the no-backend promise, so input is by drag-and-drop, file picker or pasted hex or base64. It targets broad coverage of common formats rather than the exhaustive single-format depth of dedicated PNG or PDF inspectors.

  • No upload, no server, no runtime CDN - reads files locally
  • Works offline as an installable PWA after first visit
  • No URL fetch - drag-and-drop, file picker or paste hex/base64 only
  • Breadth over single-format exhaustiveness; not every spec field is decoded
AnyTool File Anatomy Viewer vs typical online alternatives
CapabilityAnyToolTypical alternative
Privacy / no uploadYes - 100% client-sideOften server-side or login-gated
PriceFree, no signupFreemium/paywall or OAuth gate
Format coverage10+ formats auto-detectedOften single-format (PNG, PDF or ZIP only)
Tree to hex syncBidirectional, virtualizedOften hex dump only, no field tree
Validation / entropyPNG CRC-32 + Shannon entropyRarely both, often neither
Offline / mobilePWA, dark mode, mobile-firstDesktop install or not mobile-tuned

Dedicated single-format inspectors may decode one format more exhaustively.