Compare two PDF files

Comparing by eye is slow and unreliable, especially with long documents. A text comparison catches the small edits people miss:

• Contracts and leases. Check what changed between the draft you reviewed and the version you were sent to sign.
• Offer letters and policies. Spot changed numbers, dates or terms.
• Academic and technical papers. See what a co-author or reviewer revised.
• Price lists and specifications. Find which items or figures were updated.
• Regulatory or legal documents. Confirm that a re-issued version is identical, or find exactly where it differs.

The tool extracts the text from each page of both PDFs and compares them word by word, using a longest-common-subsequence algorithm (the same idea behind many diff tools). Page 1 of the original is compared with page 1 of the new version, page 2 with page 2, and so on.

The result shows:

• a summary of how many words changed on how many pages,
• each changed page with the full text,
• red, struck-through words for text removed in the new version,
• green words for text added in the new version.

Pages with no changes are skipped, so you only read what matters. If there are no differences at all, the tool tells you the text is identical.

Visual mode renders both pages at the same width and offers three views:

• Side by side, with linked scrolling: scroll one page and the other follows.
• Overlay: the new version sits semi-transparently on top of the original, and a slider sets how much of each you see. A shifted line or a moved image stands out at once.
• Difference heatmap: identical pixels are pale gray, changed pixels red; the stronger the red, the bigger the difference.

Scan all pages compares every page pair and lists the share of changed pixels for each page, so in a long document you know straight away which pages to look at.

Because pages are matched by number in both modes, inserting a whole page early in the new version shifts everything after it, and the following pages will all show differences. In that case, delete or move the extra page first (see Delete PDF pages) so the page numbers line up, then compare again.

Visual mode works on scans as they are, because it compares images rather than text. It is very sensitive to alignment, though: if the two scans were made slightly shifted or rotated, almost every pixel looks different. For a word-level comparison, run both files through OCR PDF first to add a text layer, then use text mode. OCR can introduce small recognition errors, so treat single-character differences in scanned documents with some caution.

Both PDFs are processed in your browser and never uploaded. That is important for contracts, legal drafts and business documents you may not be allowed to share with third parties. Very long pages with thousands of words take a little longer to compare.

Neither file is modified by the comparison, and nothing is saved. Remove the files or close the tab when you are done.

Your landlord sends a renewal lease and says it is the same as last year's apart from the rent. Drop last year's lease in the first box and the new one in the second, then click Compare. The summary says 9 words changed on 2 pages. On page 1 you see the old rent in red and the new rent in green. On page 4 you also see that a pet fee clause was added in green. Now you know exactly what to ask about before you sign.