How do I compare two PDF files for differences?

Add both versions to the Compare PDF tool; it extracts and diffs the text in your browser and highlights added and removed lines so you can see what changed.

Are my files uploaded to a server?

No. PDFER runs entirely in your browser using WebAssembly and JavaScript. Your files are read into memory on your device, processed locally, and never sent to PDFER or any third party. Closing the tab or leaving the tool erases them from memory.

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06 · PDF Security

Compare PDF

Compare two PDFs side by side and highlight what changed.

Local only — files never leave your browser

Drop the two versions below. Compare highlights text differences page by page — it works on selectable text, not scanned images.

Original

Revised

All PDF Security →

Compare PDF: how it works

To compare two PDFs, open the Compare PDF tool, add both files, and PDFER highlights what changed between them in your browser. Neither file is uploaded.

How to use Compare PDF

Open the Compare PDF tool.
Add the two PDF versions.
Review the highlighted differences.

In your browser vs. uploading to a server

Best for spotting edits between two versions of a contract or draft without a paid diff tool. Comparison is text-based and runs on-device.

Frequently asked questions

How do I compare two PDF files for differences?: Add both versions to the Compare PDF tool; it extracts and diffs the text in your browser and highlights added and removed lines so you can see what changed.
Are my files uploaded to a server?: No. PDFER runs entirely in your browser using WebAssembly and JavaScript. Your files are read into memory on your device, processed locally, and never sent to PDFER or any third party. Closing the tab or leaving the tool erases them from memory.

PDFER is a privacy-first PDF toolkit built by Kiril Urbonas. Every tool runs entirely in your browser — see our security model and privacy policy.