Compare PDF Files and See What Changed

1. 00

   What's great about Compare PDF

   • Everything happens in your browser. Your PDFs are never uploaded.
   • You get one PDF report. It starts with a summary and a map of every page, then shows each page with a difference, PDF 1 on the left and PDF 2 on the right.
   • Text only in PDF 1 is marked red, text only in PDF 2 is marked green, and visual differences are drawn as boxes.
   • Both PDFs sit side by side and scroll together, with the differences marked on the pages before you make the report.
   • It can compare text, how the pages look, or both, so scanned PDFs work too.
   • It works offline once the page has loaded, and there are no limits on how often you use it.
2. 01

   Add exactly two PDFs

   • Choose both PDFs, or drag them in. Only the first two you select will be added. The first card (left) is the Original and the second (right) is the Revised.
   • Type a custom name in a box above the previews if you like. Left alone, a box shows PDF 1 or PDF 2. A custom name is used on the cards and in the report, and its number shows in small text under the box.
   • If you remove one PDF with the X, a big Add PDF box appears in its place.
   • Scroll to see every page. The two PDFs scroll together, so the same page of each stays side by side.
   • If they are the wrong way round, press Swap PDFs, or drag a card to a new place.
   • With fewer or more than two PDFs, the main button stays off until you add or remove cards.
3. 02

   Choose what to compare

   • Text finds added and removed words. Visual finds changes in how pages look. Both does both.
   • Ignore case treats Hello and hello as the same.
   • Visual sensitivity sets how small a visual change can be before it is marked. If too much is marked, lower it.
   • Each page is labelled Difference Detected (red) or No Difference Detected (green). Press Jump to 1st change to scroll to the first change that was found.
   • The changes are found as soon as both PDFs are added, and again when you change an option. Text found only in PDF 1 is marked red on PDF 1, text found only in PDF 2 is marked green on PDF 2, and visual differences get a blue box.
4. 03

   Compare and download

   • When the changes are marked on the pages, press Compare PDFs to make the report.
   • When the report is ready, the button turns into Download Difference Report.
   • The report is named from the File Name box. Change the name before you download if you like.
   • If you change an option or the order of the cards, compare again to get a new report.
5. 04

   What to do next

   • Use Password Unlock PDF first if a PDF is locked.
   • Use Export PDF Text to read the text of either PDF, Remove Pages from PDF or Reorganize PDF Pages to tidy a revised file, and Merge PDF to put the report and the PDFs in one file.
6. 05

   Loved it?

   • If you're on computer, bookmark this page to your browser.
   • If you're on mobile, add it to your home screen for one-tap access and offline use.
     • Android: Visit this page in Google Chrome > tap three-dot icon (⋮) at top > Install and create shortcut. See screenshots for help.
     • iPhone and iPad: Visit this page in Safari > tap menu icon in address bar > Share > Add to Home Screen. See screenshots for help.

How it works

For text, the tool reads the words on every page of both PDFs. It lines up the paragraphs first, and only compares word by word inside the paragraphs that differ, so long PDFs stay quick. For looks, it draws each pair of pages at the same size, compares them on a small grid, and joins the cells that differ into boxes. If one page is smaller than the other, it is scaled to fit the larger one.

The report is drawn page by page as pictures and then put into a PDF. That is why it can print any script, including Hindi. When the report is ready, the tool opens it again and checks that it has the pages it should. If that check fails, no file is made.

This is a best effort. Pages are compared in order, so a page added early makes later pages look different. Scanned pages have no text, so only Visual can compare them. Highlights are placed from the text positions in each PDF and can be slightly off. A stretch with a very large number of changed words is marked as fully replaced. Very large PDFs need a lot of memory.

Frequently asked questions

• Is my PDF uploaded anywhere? No. Both PDFs are read and compared inside your browser, and the report is made there too. Nothing is sent to a server.
• Which PDF is the Original? The first card is the Original and the second card is the Revised. Drag a card to change the order, or press Swap.
• Why do both PDFs scroll together? They sit side by side in one view, so the same page of each stays level. If one PDF has fewer pages, its column ends sooner.
• Can I compare more than two PDFs? No. The tool compares exactly two PDFs at a time. To compare another pair, remove one card and add the next PDF.
• Can I compare scanned PDFs? A scan is a picture and has no text, so it can only be compared visually. Choose Visual or Both.
• Why does a page I did not change show as changed? Pages are compared in order. If a page was added early, every later page lines up with a different page and looks different. The text comparison copes better with this, because it matches text across pages.
• Can I compare a password-protected PDF? Password-protected PDFs cannot be compared. Remove the password first with PDF Password Unlock.
• Does it work with Hindi and other scripts? Yes, as far as it can. The report pages are drawn as pictures, so any script prints. Words are found by their spaces, and Chinese and Japanese are compared one character at a time. Highlights are placed from the text positions in each PDF and can be slightly off.
• How big can the PDFs be? There is no set limit, but very large PDFs need a lot of memory and take longer, because the changes are found as soon as you add the files. If the page becomes slow, close other tabs or compare fewer pages.

What happens to your file

Your PDFs are read inside your browser and compared there. Nothing is uploaded, nothing is tracked, and no file leaves your device. The report is saved straight to your device when you press Download.

How to get the most out of it

• Put the older PDF first. Removed text is read from the first card and added text from the second.
• Use Both for most PDFs. Use Text when only the wording matters, and Visual for scans.
• If a page was inserted, rely on the text result for the pages after it.
• If tiny differences in how pages were drawn get marked, lower Visual sensitivity.
• Close other tabs before comparing very large PDFs.