Compare PDFs on your computer

Review visual and text changes between two PDFs locally in your browser. Neither file is uploaded.

100% private: everything runs on your computer, your files never leave your device.

Upload the original and revised PDF
Review the pages that changed
Inspect both versions side by side

What Compare PDFs does

Compare PDFs takes two versions of a document, an original and a revised one, and tells you which pages changed. Each pair of pages is compared twice: their text is extracted and checked for any difference, and both pages are rendered and compared pixel by pixel. The result is an on-screen report with a list of the pages that differ and, for each of them, the two versions side by side with the areas of visual change outlined in orange on the revised page.

It answers a very common question quickly: what did the other party change in the contract they sent back, is this really the same invoice, did the designer touch anything besides the cover, which pages of the new edition are different. Both files are analysed in your browser and neither is uploaded.

How to compare two PDFs

Add exactly two PDFs: the first is treated as the Original and the second as the Revised version. The tool refuses to start with one file or with three.
Wait while the pages are analysed. There are no settings; the comparison starts on its own and the message Comparing PDFs is shown until it finishes.
Read the summary. Either No differences were detected, or the number of pages with changes and, if the documents have a different length, a line with both page counts.
Click through the page chips. Each one shows the page number and the kind of change: Visual change with a percentage of pixels that differ, or Text change when the words differ but the layout looks the same.
Inspect the two versions side by side. Orange rectangles outline the regions that changed on the revised page. Press Compare other PDFs to start again.

How the comparison works and what it does not do

For every page present in both documents, the text is normalised and compared as a whole, and both pages are rendered at the same size, 720 by 960 pixels, and compared with a perceptual pixel difference that ignores anti-aliasing noise. A page is reported when more than 0.02 percent of its pixels differ or when the text differs. The changed pixels are grouped into horizontal bands, which become the orange rectangles.

The report is shown on screen only. There is no downloadable difference PDF or JSON.
Text differences are flagged per page, not word by word. To see exactly which words changed, look at the two pages side by side.
Pages beyond the shorter document are not rendered; the report only tells you that the page counts differ.
Content reflow, for example a paragraph that moved to the next page, shows up as visual changes on all the pages it affected.
Scanned documents are compared as images. Small differences in scanning produce small visual percentages, so judge those results with the preview.
Password-protected PDFs are not accepted. Remove the password with Decrypt PDF first.

Privacy: both documents stay in your browser

Text extraction and page rendering are done by the PDF engine bundled with OléPDF, and the pixel comparison runs on the browser's own drawing surface. Neither file is uploaded, no page image is sent anywhere and no third-party script is loaded. The only download is OléPDF's own code from its own domain.

That is what makes it appropriate for the documents people most often need to compare: contract versions, offers, financial statements and legal drafts.

Typical uses

Checking which clauses were changed in a contract that came back from the other party with no track changes.
Verifying that a reprinted or re-exported document is identical to the approved version before signing or publishing it.
Reviewing two editions of a manual or a price list to find the pages that need a second look.

Frequently asked questions

Is Compare PDFs free?

Yes. Comparing is free and unlimited, with no account, no watermark and no daily cap.

Can I download a report of the differences?

No. The result is shown in the browser as a list of changed pages and side by side previews. Take a screenshot if you need to keep a record.

Does it show which words changed?

Not word by word. The tool tells you that the text of a page changed and highlights the areas that look different; the exact wording is for you to read in the two previews.

Why does a page show a visual change when I see no difference?

Because a small shift, a different font rendering or a re-scanned page moves pixels without changing the meaning. The percentage next to the page tells you how much actually differs.

What if the documents have a different number of pages?

The pages that exist in both are compared and a line reports both page counts. The extra pages at the end of the longer document are not shown.

Can I compare more than two files?

No. The tool works with exactly two PDFs per run. Compare the versions in pairs.

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