Need to spot what changed between two versions of a PDF contract, report, or document? PDF Compare lets you view both files side by side, drag a slider to overlay them, and run a pixel-level diff that highlights every changed region in red — entirely in your browser with zero file uploads.
Go to pdfeditor.onl/compare-pdf. No sign-up or installation required. The tool works in any modern browser on desktop and mobile.
Click the File A upload zone and select your original PDF. Then click the File B upload zone and select the revised version. Both files are loaded into browser memory only — they are never sent to any server.
Tip: You can also use the File A / File B buttons in the top navigation bar to upload or replace files at any time.
Click the Compare button. The tool renders every page from both PDFs and performs a pixel-level analysis. Changed pixels are highlighted in red on a greyscale background. The summary shows how many pages changed and the average change percentage.
Use the view mode toggle to switch between three comparison views. Side by Side shows both pages simultaneously with diff highlights overlaid. Overlay lets you drag a divider left and right to reveal File A or File B on the same canvas. Diff shows the pixel-level result with red regions marking every change.
Tip: Changed pages are marked with an amber percentage badge in the page navigation strip — jump directly to the pages with the most changes.
Click Download Page X to save the current page diff as a PNG, or click Download All Pages as PDF to export every diff page into a single PDF report. The PDF can be shared or attached to an audit trail.
Each page is rendered as an image at high resolution. The tool compares every pixel between the two versions. Pixels that differ by more than a small threshold are highlighted in red on a greyscale background, making even subtle changes immediately visible.
Yes. If File A has 10 pages and File B has 8 pages, the extra pages from File A are treated as 100% changed. The summary shows the total pages, changed pages, identical pages, and average change percentage.
The overlay slider places both PDF versions on the same canvas. Drag the divider left to reveal more of File B and right to reveal more of File A — the fastest way to spot layout shifts, text repositioning, or image replacements.
Completely. All rendering and comparison runs inside your browser using WebAssembly and PDF.js. Your files are never uploaded to any server. When you close the tab, everything is cleared from memory.
Yes. Click Download Page X for a PNG of the current diff page, or Download All Pages as PDF to get a complete diff report as a PDF file — one diff page per PDF page.
Any visually rendered difference — text changes, font changes, image swaps, layout shifts, added or removed content. It works on digitally created and scanned PDFs alike.