Compare PDFs
Choose an original and a changed PDF to get a summary of which pages are the same or different, and for each changed page the removed and added lines with the changed words highlighted. The text is read in your browser, so the documents stay private.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Choose the original PDF in the first box and the changed version in the second.
- Read the summary: how many pages are the same, changed, or exist only in one file.
- Open a changed page to see its removed lines (marked with −) and added lines (marked with +). Changed words are highlighted.
- Switch the ignore options if differences in case or spacing are not important to you.
How it works
The text of each page is extracted with the PDF engine used by browsers and split into lines. For each page number the two texts are compared with the same difference algorithm as the Text diff tool: it finds the shortest list of line removals and additions, then compares the removed and added lines word by word. A page counts as changed when at least one line differs. Pages that exist in only one file are listed as such, with their lines. Each page shows at most 200 changed lines; the counts stay exact.
Worked example
If page 1 of A says Hello world and page 1 of B says Hello brave world, the page is changed with one line removed, one added, and the word brave highlighted. A page with identical text is listed as the same.
Tips
- Compare exports from the same program for the cleanest results; different programs can break lines differently.
- Use the Text diff tool if you want to compare pasted text instead.
Frequently asked questions
What exactly is compared?
The text of page 1 of A against page 1 of B, page 2 against page 2, and so on. Lines are compared first, and in a changed line the differing words are marked. Images, layout, fonts, colors and annotations are not compared.
Can it compare scanned PDFs?
Not unless they already have a text layer. A scan is a picture of a page, with no text to read, and the tool says so. Run optical character recognition first, then compare.
Why do pages show as changed when I only added a paragraph?
Pages are compared by number. Text inserted early moves everything after it onto later pages, so following pages can show as changed even though the words are the same. Read the highlighted lines to see the real change.
What do the ignore options do?
Ignore upper and lower case treats Word and word as equal. Ignore extra spaces trims lines and collapses runs of spaces, which helps because PDFs often differ in spacing only.
Is anything uploaded?
No. Both PDFs are opened and their text is extracted inside your browser.