About compare PDF files
Two comparison methods exist because they answer different questions, and choosing wrong wastes your time. A text diff extracts the text layer from both files, aligns the two sequences with a longest-common-subsequence algorithm, and reports insertions and deletions precisely — one changed number in a forty-page contract is found exactly. It is completely blind to presentation: a document reset in a different typeface with every margin altered will diff as identical, because the words did not change. A visual comparison renders both documents to bitmaps and compares pixels, so it catches moved images, restyling and layout shifts — but it flags harmless reflow too, because one inserted word early on can shift every line after it and make whole pages "differ". Start with text when you are checking wording, and use visual only when appearance is what is under review. Both run locally on both files.
How to compare PDF files
- 01
Add both PDFs
Drop in the original first and the revision second — the order determines what counts as an insertion.
- 02
Choose the method
Text for wording, visual for appearance. If unsure, run text first; it is faster and more precise.
- 03
Set granularity
Word suits prose, line suits structured or tabular documents, character catches single-digit edits.
- 04
Read the report
Differences are listed per page with their context so you can judge which ones matter.
What this tool does
- Two genuinely different methods rather than one compromise
- Longest-common-subsequence alignment, so a moved paragraph is not reported as a wholesale rewrite
- Word, line and character granularity for the text diff
- Whitespace-insensitive by default, so reflow does not drown out real changes
- Both documents stay on your device — appropriate for contracts under negotiation
Limitations worth knowing
Every PDF tool has constraints. Stating them plainly is more useful than discovering them halfway through your work.
- A text diff cannot see formatting, fonts, colour or layout changes at all.
- A visual diff reports reflow as difference: one inserted word can make every later page differ.
- Scanned PDFs with no text layer can only be compared visually, or must be OCR'd first.
- Visual comparison renders both files, so it is substantially slower and more memory-hungry than a text diff.
How your file is handled
This tool runs entirely inside this browser tab. When you choose a file, your browser reads it from your own disk and hands the bytes to JavaScript running on this page — no network request carries your document anywhere. You can confirm that yourself: open your browser’s developer tools, switch to the Network panel, and run the tool. You will see no upload.
Nothing is stored after the fact. Closing or reloading this tab discards the file, the result and everything derived from them, because none of it ever left your machine. Read how local processing works.
Questions about compare PDF files
Which method should I choose?
Text when the question is "what wording changed" — contracts, policies, specifications. Visual when the question is "does this look different" — branded material, layouts, anything where appearance is the deliverable.
Why does the visual mode say almost every page differs?
Reflow. Insert a sentence on page two and every subsequent line moves down, so the pixels differ even though the content is unchanged after that point. A text diff is the right tool in that situation.
Can I compare two scanned documents?
Visually, yes. A text diff needs a text layer, so scans return nothing until you OCR them — and note that OCR errors then appear as false differences.
Does file order matter?
Yes, for interpretation. The first file is treated as the original, so additions and removals are expressed relative to it. Swapping them inverts the report without changing what it found.
Are both files uploaded to be compared?
No. Extraction, rendering and comparison all run in your browser tab, which is what makes this usable for documents under legal privilege.
Tools that pair with this one
- Compare PDF TextOnly the words, so a reformatted document still reads as unchanged.
- Visual PDF ComparisonCompare what the page looks like, not just what it says.
- PDF Text DiffDiff semantics applied to PDF text, at word granularity.
- Highlight PDF DifferencesA shareable PDF with the changed regions marked on the page.
- Extract Text from PDFLift the text layer out of a PDF and keep it in reading order.
- PDF InspectorA complete technical report on any PDF, produced without uploading it.