# Compare PDF Files

> Two versions of a contract, one diff view. The viewer lays the documents side-by-side or as a single overlay with a draggable slider, and highlights every region of changed pixels in red. A separate Text Diff modal opens word-level changes line by line. Both source files stay in the browser tab — useful when the diff includes deal terms, manuscript revisions, or design proofs that shouldn't touch a vendor's server.


Live tool: https://lofttools.com/tools/pdf-tools/compare-pdf

Category: PDF & Documents


## What it does

- Side-by-side and overlay diff modes with draggable slider
- Word-level text diff with line numbers in a modal (split or unified)
- Pixel-level layout diff highlights — covers reflow, spacing changes, and image shifts (anything that changes the rendered page)
- Page rail with per-page diff badge + A/B preview stack
- Right pane comparing metadata, bookmarks, form fields, and fonts side-by-side
- Apple-style transparent ruler overlay with px / in / mm units
- Drag-rect exclusion zones to ignore page numbers / timestamps / margins
- Jump-to-next-change with F7 / Shift-F7
- Multi-page PDFs handled in browser memory (no per-page upload)
- Both source files stay in the browser tab — no server upload

## How it works

1. **Drop two PDFs in the splash** — Drop or pick an Original and a Modified PDF. Comparison fires automatically once both files are loaded.
2. **Compare** — Pixel diff with smart morphology runs in your browser; differences in text, images, and layout are highlighted on every page.
3. **Navigate changes** — Use the page rail, F7 to jump to the next change, or open the line-numbered text diff modal.

## FAQ

### What types of differences are detected?

Text additions, deletions, and modifications are highlighted. Layout and image changes are also shown.

### Does this preserve bookmarks and form fields?

Yes. The output PDF inherits bookmarks and form fields from the chosen base document; the diff overlay is added as annotations.

### What PDF versions are supported?

PDF 1.0 through 2.0 are diffed page-for-page. Encrypted files need to be unlocked first.

## Privacy — what we do not do

This tool runs entirely in the browser via WebAssembly. Your file never reaches a Loft Tools server. Specifically:

- **No upload.** The file bytes load into the browser tab's memory and process on your own CPU. Open DevTools → Network and observe zero outbound requests carrying file data while Compare PDF Files runs.
- **No AI training on your file.** Loft does not train models. We could not train on a file we cannot see.
- **No content scanning.** No virus, copyright, or content-moderation pass against your file. The bytes are not accessible to us.
- **No server-side log of file contents, filenames, or EXIF metadata.** Cloudflare edge captures URL and truncated IP for abuse defense (standard CDN behaviour). Cloudflare Web Analytics records anonymous page hits, no cookies, no PII. Nothing about your file content reaches any log.
- **No retention.** Close the tab and the file leaves browser memory. No backups exist on our side because no copy ever existed on our side.
- **No account.** No email, no signup, no auth, no telemetry tied to you.
- **Offline-capable after first visit** (PWA). Once you've loaded a tool, it caches; later sessions work without internet. For high-sensitivity files, run the tool once online to warm the cache, then disconnect before processing.

Compare with upload-based services: each transmits your file to a processing server. Even over HTTPS, each has logs, retention windows, and subpoena exposure. Loft has none of these because the server architecture does not include your file.

## More

- All tools: https://lofttools.com/tools
- Category: https://lofttools.com/tools/pdf-tools
- LLM index: https://lofttools.com/llms.txt