How to compare two PDFs
- Add File A. Drag your first PDF onto the left box or click to browse. The tool reads it on your device and shows the page count.
- Add File B. Do the same for the second PDF in the right box, the version you want to check it against.
- Pick a sensitivity. Standard works for most documents. Choose Low to ignore small rendering noise, or High to catch subtle changes.
- Press Compare PDFs. Every page pair is rendered and diffed, then a summary tells you how many pages differ.
- Step through pages. Use Prev/Next to move page by page, and switch the view between diff highlight, side by side, or just one file.
When comparing PDFs actually matters
Redlining a contract by eye is slow and error-prone, especially past page ten. Before signing a revised agreement, running the old and new versions through a visual comparison shows you at a glance which pages actually changed, so you know exactly where to focus your read instead of rereading the whole document from the top. The same idea applies to revision tracking on proposals, statements of work, and policy documents that pass through several rounds of edits: a quick page-by-page check confirms nothing moved that shouldn't have.
It is also useful outside of legal paperwork. If you reprint a form, regenerate an invoice template, or export the same report from two different tools, comparing the output against a known-good original tells you whether the reprint is truly identical or whether a margin, font, or layout shifted along the way. Print shops and design teams use the same trick to check a proof against a previous approved version before a job goes to press.
How the visual comparison works
Each page of File A and the matching page of File B is rendered to an image at the same width, so both pages line up pixel for pixel regardless of the PDF's original size. The tool then walks through every pixel in that pair of images and checks how far apart the colors are. Any pixel that differs by more than the chosen sensitivity is painted red on a third "diff" image; everything else is shown as a dimmed, grayscale version of the original page so the red marks stand out clearly. Do this for every page, and you get an instant visual map of exactly where the two files disagree, one image per page, that you can click through.
If File A and File B have a different number of pages, the tool compares as many pairs as it can and clearly lists which trailing pages in the longer file have no counterpart to compare against. If a page in one file has noticeably different proportions from its counterpart, for example one is portrait and the other landscape, that is called out too, because a shape change is itself a meaningful difference worth knowing about.
What this tool does not do
Be clear about one thing: this is a visual, pixel-level comparison, not a word-level text diff. It compares what each page looks like, not what the underlying text says. That means if the exact same paragraph gets reflowed onto a slightly different layout, for example because a header got taller or a font changed, the page will show up as "different" even though not a single word actually changed. For a true word-by-word comparison of two blocks of text, use a dedicated text diff checkerinstead. Use this tool when you specifically want to know whether two PDFs look the same, not just whether they say the same thing.
Frequently asked questions
Does this show what text changed?
No. This is a visual, pixel-level comparison, not a word-level one. It highlights where the two pages look different, but it does not tell you which words were added, removed or edited.
Is my file uploaded anywhere?
No. Both PDFs are opened and rendered entirely in your browser. Nothing is uploaded to a server.
Why does a page show as different when the words look the same?
Because the comparison looks at pixels, not text. If the same words are reflowed onto a different layout, moved a few points, or set in a different font, the page will look different even though the wording is unchanged.
Is there a limit on how many pages it compares?
To keep large documents responsive in your browser, comparisons stop after 60 pages. The tool tells you if a file was cut off.
Related: text diff checker · merge PDFs · sign PDF.