PDFMonks

Compare two PDF files

Earlier PDF or drop it here
Later PDF or drop it here
Choose an earlier PDF and a later PDF first.

Compare an earlier PDF with a later version without uploading either file. The tool aligns inserted and removed pages, then compares every aligned page as selectable text and as rendered pixels, so an empty text layer cannot pass as identical. Choose any result to see both pages and the words added or removed. The downloadable report is read back and checked. Both PDFs stay in this browser tab with no upload and no account.

How to compare two PDF files online

  1. Choose both PDFs

    Choose the earlier PDF and the later PDF, or drop each file into its marked area. Both files stay in this browser tab.

  2. Compare the versions

    The tool reads selectable text from both files, aligns matching pages and renders every aligned page pair before it counts inserted, removed and changed pages.

  3. Inspect each change

    Choose a result in the page map to see both rendered pages, changed regions and the words added or removed. The word comparison ignores capitalization and repeated whitespace.

  4. Download the report

    The tool reads the generated HTML report back and checks that every aligned page and result survived before the download appears.

What this comparison means

The word comparison ignores capitalization and repeated whitespace. The page preview marks rendered pixel regions that differ. Complex layout changes can produce a large region even when the visible edit is small. A page that moved a paragraph down by one line will show a changed region covering both the old and new positions, even though the text is identical.

The report is a page map, not a legal redline. Review signatures, forms, annotations and print-production changes in the source PDFs when those details matter. To find the differences between two versions of one document, read the page map first and open the sources only where it says something moved.

Where comparing PDFs fits

A comparison answers one question: what changed between the copy you had and the copy you were sent. Contract redlines, a specification returned by a supplier, a policy reissued with no changelog, a report regenerated after a data fix. In each case the document is long, the change is small, and reading both versions side by side is the slow way to find it.

Two comparisons run on every aligned page, and they check each other. The text comparison reads the selectable characters and reports the words added and removed. The pixel comparison renders both pages and reports where the ink differs. A page that looks identical but reads differently, or reads identically but looks different, is reported rather than passed, which is why a scanned page with an empty text layer cannot slip through as unchanged.

Comparing is a read-only operation: neither file is modified, and neither leaves this browser tab. When you know what changed and want to act on it, How to edit a PDF covers what a browser tool can and cannot change, and Edit text in a PDF explains why replacing a sentence in place is harder than it looks. To read a version as plain text and diff it with your own tools, use PDF to Markdown. To check whether a stamped or signed version matches the original, run the comparison before and after the change.

What the ranking comparison tools offer

The ranking pages for this query split into two camps. Draftable's online tool shows differences as a redline or side by side with a change list and PDF export, and asks desktop-size screens for the web version; its comparison also detects style changes like font, size, bold and italics. The diff.tools PDF comparator runs entirely in the visitor's browser like this one, adds built-in OCR for scanned pages, page-range selection and a one-click jump to a plain-text diff - but names only Chrome and Edge as supported browsers. Those are their pages' claims, not measurements made here.

The other camp collects both files first: Sejda's compare page walks through uploading two PDFs to see every text change side by side, while also promising private in-browser comparison on the same page. Tools that take uploads typically promise deletion after a window - PDFCandy names 2 hours on its BMP page, Smallpdf one hour on its compressor page. Here both PDFs stay in the tab from the start, and every aligned page gets two independent checks - selectable-text words added or removed, plus rendered-pixel regions that differ - so a page that reads the same but looks different, or looks the same but reads differently, is reported rather than passed. What this tool does not do is OCR: a scanned page is compared from its rendered pixels, which finds visual changes but cannot list the words.

Questions about comparing PDFs

Do the PDFs leave my browser?
No. Both PDFs are opened, aligned, rendered and checked in this browser tab. Neither file is uploaded to a server.
What happens when a page was inserted?
The page aligner creates an inserted row instead of treating every later page as changed. Removed pages get their own rows too.
Can it compare scanned PDFs?
Yes. Pages without selectable text are compared from rendered pixels. They are not called identical from an empty text layer.
What text changes does it show?
For each aligned page, the tool lists words added to the later PDF and words removed from the earlier PDF. The comparison ignores capitalization and repeated whitespace.
Does it change either PDF?
No. The two source files remain unchanged. The only output is a standalone HTML comparison report.
What does the report check prove?
The generated report is read back in this tab. Its row count and every page result must match the comparison before download is enabled.
Can I compare more than two PDFs at once?
No. This tool compares two PDFs: an earlier version and a later version. To compare multiple drafts, run successive pairwise comparisons or export each to text with PDF to Markdown and diff them yourself.
Is there a file size limit?
No hard limit. The tool runs in your browser, so the practical limit is the memory of your device. Very large PDFs take longer to render but are not rejected.

The other pdfmonks tools

They all run in a browser tab like this one. Each reads its own output back and checks it before offering the download, and none of them needs an account.

Where to go next