Every difference between two versions of a document.
Open the old file and the new one — DocDiffer lines the paragraphs up and marks every word that was added, removed or rewritten, without uploading anything.
The earlier version
Drop the document here — or choose it from your device.
PDF, DOCX, TXT, Markdown, RTF — up to 80 MB, read on this device
The newer version
Drop the document here — or choose it from your device.
PDF, DOCX, TXT, Markdown, RTF — up to 80 MB, read on this device
Both documents are opened and compared inside this browser tab. Nothing is uploaded, and closing the tab clears everything.
Why DocDiffer
Two levels at once
Paragraphs are aligned first, so a clause that moved stays matched with itself. Inside every rewritten paragraph the words are diffed again and marked in place — you see which clause changed and which word inside it did.
The formats documents arrive in
PDF text is rebuilt page by page from positioned runs, DOCX is read through its real paragraph, heading and table structure, and TXT, Markdown and RTF are taken as they are. You can compare a DOCX draft against the PDF that was signed.
Noise you can switch off
Whitespace, letter case, punctuation and quote style, and the running headers that repeat on every page can each be ignored. A document re-exported by another program stops looking like a hundred edits.
A reference for every change
Each change carries its page and paragraph number, so it can be quoted in an email or found in the original. The full list exports as text, Markdown or a printable web page — the report leaves your device, the documents never do.
About DocDiffer
DocDiffer is a document diff that runs in the browser. It compares two versions of a contract, a report, a policy, a manuscript or a translation and shows what changed between them: paragraphs that were added, paragraphs that were removed, and the exact words that were rewritten inside the ones that stayed. It reads PDF, DOCX, TXT, Markdown and RTF, in any combination, so you can compare two Word documents online, compare two PDFs, or check a draft against the version that was actually signed. Every change is listed with its page and paragraph reference, and the list can be filtered down to additions, deletions or rewrites alone.
The comparison happens entirely on your device. The browser opens both files, rebuilds their text — PDF pages through pdf.js, DOCX through its XML structure — aligns the paragraphs and marks the differences; nothing is sent anywhere, and there is no server that could store a copy. That matters for the documents people usually need to compare: contracts under negotiation, medical and financial paperwork, unpublished manuscripts. What DocDiffer compares is text, not layout, so fonts, margins, colours and comments are outside its scope, and a scanned PDF without a text layer has to go through OCR first. Everything else — the report, the counts, the references — you can export and keep.
Guides & articles
How to read a redline, what Track Changes hides, and why PDF text never extracts cleanly.
Comparing contract versions: what to look for beyond the obvious edits
The dangerous edits in a contract are rarely the ones in the covering email. Here is the checklist a reviewer runs through when a new version lands.
Track Changes vs an independent diff: why you should verify redlines yourself
Revision marks show what someone chose to show you. Comparing the two files compares what is actually in them — and the two answers are not always the same.
Why PDF text extraction is imperfect: columns, ligatures, scanned pages and hyphenation
A PDF does not contain paragraphs. It contains instructions for placing glyphs on a page — and everything a comparison tool knows about your text is reconstructed from them.
Frequently asked questions
Are my documents uploaded anywhere?
No. Both files are opened by the browser itself and compared by JavaScript running in this tab. There is no upload, no account and no server that could keep a copy — the site is a set of static files, and after the page has loaded it works offline. Close the tab and everything you opened is gone.
Which file formats can I compare?
PDF, DOCX, TXT, Markdown and RTF, in any combination — you can compare a DOCX draft against the PDF that was signed. You can also paste text straight into either side, which is the quickest way to check two clauses or two translations against each other. Legacy .doc files and Pages or ODT documents are not supported; export them to DOCX or PDF first.
Can it compare a scanned PDF?
Only if the scan has a text layer. A PDF made by a scanner or a photo of a page contains an image, not characters, so there is nothing to extract and DocDiffer will tell you that no text was found. Run the file through OCR first (most scanner apps and PDF readers can add a searchable text layer), then compare the OCR'd copies — and read the result with the usual OCR caution about numbers and single characters.
Does it compare formatting, or only the text?
Only the text. Fonts, colours, margins, styles, comments and tracked-change marks are not part of the comparison — DocDiffer reduces both documents to a sequence of paragraphs and compares those. That is deliberate: a document re-exported from a different program can differ in almost every formatting attribute while the wording is identical, and it is the wording that decides what you agreed to.
What happens to tables?
Each table row becomes one paragraph, with the cells joined by a vertical bar, so a changed figure in a price table shows up as a rewritten row with the old and new number marked. Cell merges and nested tables flatten, and a table that was reordered will read as several removed and added rows rather than as a move.
How accurate are the counts in the summary?
They count paragraphs and words as DocDiffer sees them after extraction, which is exact for DOCX and text files and approximate for PDF, where paragraphs have to be rebuilt from positioned text runs. A paragraph that was moved from one page to another usually counts as one removal plus one addition, because the comparison keeps document order. Treat the numbers as a reliable measure of how much changed, not as a legal statement.
Can I save or share the result?
Yes — the change report can be downloaded as plain text, Markdown or a self-contained HTML page listing every change with its page and paragraph reference. The HTML version keeps the strike-through and underline marks, so it opens in any browser and prints as a readable redline. You can also copy the one-line summary for an email or a ticket.
How large a document can it handle?
Files up to 80 MB are accepted, and a few hundred pages compare comfortably on a normal laptop; the work is split into chunks so the page keeps responding, and a progress bar shows where it is. Very large documents cost memory rather than time — if a comparison feels heavy, switch the detail level to sentence or paragraph, which skips the word-level pass inside every rewritten paragraph.
Why does a re-exported PDF show changes I never made?
Because the text was rebuilt differently: another PDF engine can break lines in new places, turn quotes into typographic ones, split ligatures, or move a running header. Switch on "ignore whitespace", "ignore punctuation and quote style" and "ignore running headers and footers" in Settings — that usually removes the entire phantom diff and leaves the real edits.