Compare PDF files online

How to compare two PDF files

Choose the older PDF as A and the revised PDF as B. Start with text and visual appearance, then select how pages should be paired. Press Compare both PDFs. The report separates changed pages, pages with no differences detected, and pages that could not be assessed. Select a page pair to review the actual previews and extracted text changes.

Use the wipe view to reveal one version over the other. The side-by-side view keeps the files separate and can synchronise scrolling. When you have checked the page pairs, download a visual PDF report or export the findings as JSON, CSV or plain text. Neither original file is edited.

Text differences and visual differences are not the same

Text comparison looks at the selectable text extracted from the PDF. It can show added or removed words, numbers and punctuation. Whitespace is ignored by default, and you can choose whether letter case matters. Font encoding, reading order, hidden OCR text and unusual layouts can affect extraction. A scanned page without a text layer is not assessed in text-only mode.

Visual comparison renders pages onto a common canvas at the chosen resolution. It checks pixel colour differences above your tolerance and groups nearby changes into approximate boxes. A shifted paragraph, a changed image or a different signature appearance may show up visually even when extracted text is unchanged. Those boxes are not precise semantic edits, and no automatic signature verification is performed.

Comparing scanned PDFs and rotated pages

Use visual appearance for image-only scans. If text matters, optionally enable OCR Assist so image-only pages can contribute recognized text to page matching and text comparison. OCR can misread characters, so visual evidence remains important. Small scan or render shifts can be compensated automatically, and the revised PDF can be rotated for comparison without changing the original file.

At 144 DPI, finer differences are sampled than at 96 DPI, with more memory and processing work. Increasing colour tolerance may reduce mild scan noise but can also hide light-coloured edits. The report records the setting so that a reviewer can understand the scope of the result.

Ignore a changing header or footer deliberately

Optional top and bottom margins can exclude a timestamp or page number from comparison. Enter the margins in PDF points: 72 points equal one inch. These margins affect visual comparison and text whose baseline is inside the ignored area. Do not exclude a header containing a meaningful revision date or reference number unless that is intentional. Exclusions appear in downloaded reports.

Page ranges, insertions and missing pages

Page-order pairing is the clearest starting point for files with the same structure. Smart alignment scores text and a small visual fingerprint while keeping page order; exact-text alignment remains available when you want conservative unchanged-text anchors. Manual pairing allows a selected comparison such as 1:1, 2:- and -:3. A dash means a page is absent on that side. Pages you leave out of a manual list are explicitly outside the review.

Privacy, supported files and practical limits

The documents are processed in your browser, without an account or a conversion service. PDF libraries are hosted with UVs Tool Hub and load after you choose a document. This tool does not save an automatic recovery copy. Reloading or clearing the session removes the current comparison; downloaded reports remain wherever you save them.

Each file can contain up to 60 pages and be up to 50 MB. There are also rendering and total-pixel limits to reduce the risk of exhausting browser memory. A large-format drawing can reach those limits before a normal A4 document. Lower the comparison resolution or use Split PDF to prepare a smaller part. For private content that must be removed before sharing, use PDF Redactor; comparison highlighting is not redaction.

Frequently asked questions