Side-by-side diff for two PDFs
Drop two versions to see what changed: edited text and values, redrawn drawings, and content hidden from view. Drawing sets pair sheet by sheet, and Create report makes a PDF, Word or HTML report of every change.
- Up to 100 MB each
About Compare PDF
Two versions of a contract — or two revisions of a drawing — in one diff view. Drop both files; one engine reads each into a structured model and compares the models, so a note that moved to another column, a view nudged to make room, or a dimension label slid along its line reads as "moved", a changed value lights up only the changed digits, and an added hole or a lengthened outline highlights only that geometry. Side-by-side or overlay with a draggable slider; a separate Text Diff modal shows word-level changes. Both files stay in the browser tab — nothing touches a server.
What it does
- One engine for every PDF — contracts, statements, forms, drawings and scans, with no document-type picker
- Moves reported as moves — a relocated note, view, label or paragraph is one entry with the distance shown, not a delete plus an insert
- Nearby changes on a drawing grouped — a part added with its labels and wires is one change with its pieces inside; drawn-only changes in their own lane
- Every text edit kept — case and hyphen edits, and clipped or off-page text listed with the reason it can't be seen; font changes are not listed
- Callouts keep their identity — a slid dimension label is a move, a changed value lights up only the digits, a re-pointed arrow reads "retargeted"
- Vector geometry compared as geometry — an added hole or a lengthened outline highlights only that path or segment
- Edited images show the edited region, form fields on every page, and annotations in their own category
- Pages pair by content, so an inserted sheet does not cascade into "changed"
More features
- Change-location tags — every change labelled with its sheet region and X/Y position
- Share a receipt link that anyone with the same two files can check in their own browser
- Side-by-side and overlay diff modes with draggable slider
- Word-level text diff with line numbers in a modal (split or unified)
- Page rail with per-page diff badge + A/B preview stack
- Right pane comparing metadata, bookmarks, form fields, and fonts side-by-side
- Per-document transparent ruler (independent left/right) with px / in / mm units
- Export the marked-up comparison as a PDF
- Hidden content named — a change no reader can see is listed with its reason (hidden layer, covered, white text, off the page, tiny, invisible), with a panel of what each file hides and an X-ray view
- Earlier versions saved inside a file found and compared, first against last
- Values list — every changed number, date, amount and dimension in one place
- Review marks — Reviewed, Follow-up, a star and a note per change, with J/K/Space keys and a progress count
- Drawing sets compared sheet by sheet, paired by title-block sheet number, with a sheet map and revision-cloud counts
- Layers matched by name, with as-opened, as-printed and all-layers views
- Signatures checked in the browser — coverage, content added after signing, and the signed version compared against the current file
- Create report as a typeset PDF, Word or HTML: every change with its words and pictures, a sheet index or a redline
- Drag-rect exclusion zones to ignore page numbers / timestamps / margins
- Scroll to zoom, jump-to-next-change with F7 / Shift-F7
- Multi-page PDFs handled in browser memory (no per-page upload)
- Both source files stay in the browser tab — no server upload
How to use Compare PDF
Drop two PDFs
Drop or pick an Original and a Modified PDF. Comparison fires automatically once both files are loaded; there is no mode to choose.
Compare
Each file is read into a structured model in your browser and the two models are matched; adds, removes, edits and moves are highlighted on every page.
Navigate changes
Use the page rail, F7 to jump to the next change, or open the line-numbered text diff modal.
Frequently asked questions
What types of differences are detected?
Added, removed, modified and moved text; added, removed and changed vector geometry down to the segment; edited images; form-field values on every page; annotations; inserted, removed and reordered pages.
Can it compare engineering drawings or blueprints?
Yes, with no mode to pick. Dimensions and leaders are recognised by their value and the feature they point at, so a label that slid along its line is a move, a changed value lights up only the changed digits, and an arrow re-pointed at another feature reads "retargeted". A view nudged to make room for a note is one move, not a red-and-green blot. Each change is tagged with its sheet region and X/Y position.
What about scanned PDFs?
A page with no text layer is read by OCR in your browser (the OCR models download on first use and are cached), so a scanned revision compares text to text against the original. Such changes carry the OCR confidence and an OCR badge in the list; a line OCR cannot read stays a limit, and drawing geometry is not compared against a scan.
Does this preserve bookmarks and form fields?
Yes. The output PDF inherits bookmarks and form fields from the chosen base document; the diff overlay is added as annotations.
How large can the files be?
A drawing set can be up to 150 MB per file on a computer, because it is compared sheet by sheet; other PDFs up to 100 MB per file, and every file on a phone or tablet. A set that large uses about 10 GB of memory while it is compared, so the tool says so and waits for you to start it.
What PDF versions are supported?
PDF 1.0 through 2.0 are diffed page-for-page. Encrypted files need to be unlocked first.
What does a receipt link hold?
The change counts by kind, page counts, file sizes, both files' SHA-256 fingerprints, a digest of the result, and the tool version, engine, build and date. It holds no file names and no document text. Anyone with the same two files opens the link, adds the files, and the page compares them in their browser to show whether the result matches.