Compare PDF — Find Differences Between Two PDFs
Browser tool that compares two PDFs page by page with a word-level text diff and a pixel comparison
Runs in your browser · nothing is uploaded
Both files are opened and compared only in this browser.
A — original
Drop the original PDF (A) here
One PDF (up to 100 MB). The file never leaves your browser.
B — file to compare
Drop the PDF to compare (B) here
One PDF (up to 100 MB). The file never leaves your browser.
Higher counts even faint colour changes as different. Use Low when a re-saved file only shifted colours slightly.
Add both files.
What it does
Find what changed between two similar PDFs: a contract revision, a new version of a quote, a corrected manuscript. Add the original (A) and the file to compare (B) and press Compare, and every page is reported as the same or different. For a different page, open Details to see the word-level text changes (removed words in red strikethrough, added words underlined in green), both page images and a difference image with the changed pixels in red.
How to use
- Add the original PDF (A) on the left and the PDF to compare (B) on the right. Enter the password if a file asks for one.
- Under Compare, choose text, appearance or both (both by default).
- With the appearance comparison on, choose the sensitivity (Normal by default).
- Press Compare. Progress is shown page by page and you can Stop.
- Open Details on pages that differ. Show only pages that differ hides the rest.
How it works
- Text: PDF.js extracts each page’s text and lines are rebuilt, then compared word by word with jsdiff (BSD-3-Clause), the same engine as Text Diff. Word boundaries come from the browser’s Intl.Segmenter, so Korean, Chinese and Japanese are compared by word too; whitespace changes are ignored.
- Appearance: both pages are drawn at 100 dpi on a canvas the size of A’s page and compared with pixelmatch (ISC). Low, Normal and High sensitivity use colour thresholds of 0.2, 0.1 and 0.03. The share of differing pixels is shown as a percentage.
- Page size: pages more than half a point apart in size are flagged “page sizes differ” and are not compared pixel by pixel.
- Pairing: pages are paired by number; moved pages are not detected.
- Limits: up to 100 MB per file. Long files take a while; only the images of differing pages are kept in memory.
Examples
| Change | Result |
|---|---|
| Term changed from 12 to 24 months | Page 3 different · words +1 −1 |
| Stamp added to the signature box | Page 5 different · 0.8% of pixels differ |
| Two appendix pages added at the end | 2 page(s) only in B |
| Two identical files | No differences found |
To compare pasted text, use Text Diff; to compare two photos, use Image Diff.
FAQ
Are my files uploaded?
No. Both files are opened and compared in your browser only, so even confidential contract revisions can be compared without uploading them.
What if pages were added or removed?
Pages are compared by number. If one file is longer, its extra pages are marked "Only in A" or "Only in B". A page inserted in the middle makes every later page look different, so split the files to matching ranges first in that case.
What is the difference between the text and the appearance comparison?
The text comparison extracts the text stored in the PDF and finds added and removed words. The appearance comparison draws both pages as pictures of the same size and compares them pixel by pixel, which also catches changes in scans, stamps, pictures and table lines.
The content is the same but pages are reported as different.
Re-saving a file in another program can shift fonts or colours very slightly. Set the appearance sensitivity to Low, or compare text only.
Can it compare password-protected PDFs?
Yes. When a file asks for a password, a password field appears under it. The password is used only to open the file and is not stored.
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