Free PDF Comparison Tool — Compare Two PDFs Side by Side Online

PDF Comparison Guide

Why Use an Online PDF Comparison Tool?

Identifying what changed between two versions of a contract, report, or academic paper is time-consuming when done by eye. One missed sentence can mean a missed clause, a compliance risk, or an unattributed edit. When you need to compare PDF versions, our online PDF diff tool extracts the full text from both documents and runs a precise comparison algorithm — highlighting every addition and deletion in seconds.

• Side-by-side diff view: Original on the left with removals in red; revised on the right with additions in green.
• Word, line, and paragraph modes: Choose the granularity that fits your document type.
• 100% private: Text extraction and diffing happen entirely in your browser — no files are sent to any server.
• No account required: Open the page, upload two PDFs, and compare. No sign-up, no email, no watermarks.
• Instant stats: See a summary of how many words or lines were added and removed at a glance.

How to Compare Two PDF Files for Differences

The process takes under a minute. Follow these three steps.

Step 1: Upload Both PDFs

Drop your original document into the "PDF A" zone and your revised document into "PDF B", or click each zone to browse. Files can be up to 50 MB each. Nothing is transmitted to any server — all processing is local to your device.

Step 2: Choose Your Comparison Mode (Word, Line, or Paragraph)

Select Words to highlight individual word changes (best for contracts and prose), Lines to compare line by line (best for code or structured text), or Paragraphs for a high-level block view (best for long reports).

Step 3: Review the Diff

Click "Compare PDFs" and the tool will extract text from both documents and compute the difference. You'll see a summary of additions and removals, then a full side-by-side view with changes colour-coded — red strikethrough for removed text, green highlight for added text.

PDF Compare Tool: Key Features

Word-Level, Line-Level, and Paragraph-Level Diffs

The tool uses a proven diff algorithm to compare text at three levels of granularity. Word-level diffing is ideal when contracts or reports are revised sentence by sentence. Line-level diffing suits structured content like legislation or data tables. Paragraph mode shows which major blocks have been added, moved, or removed in long documents.

Full Privacy — No Server Uploads

Every step — text extraction via the PDF rendering engine, the diff computation, and the display — runs inside your browser tab. Your documents are never transmitted over the network. This makes the tool safe for NDAs, client contracts, medical records, and any sensitive material you cannot share with a cloud service.

Works on Any Device

The PDF comparer works on Chrome, Firefox, Safari, and Edge — on Mac, Windows, Linux, iPhone, and Android. No app installation required. As long as JavaScript is enabled, the tool works.

Frequently Asked Questions

How do I compare two PDF files for differences?

Upload your original PDF into the "PDF A" zone and your revised PDF into "PDF B". Choose a diff mode (Words, Lines, or Paragraphs) and click "Compare PDFs". The tool extracts text from both and highlights every change side by side.

Is this PDF comparison tool free?

Yes — completely free. No account, no subscription, no watermarks. Adobe Acrobat charges for this feature; QuickTooly does not.

Are my PDFs safe to upload?

Your files never leave your device. All text extraction and comparison happens inside your browser using local JavaScript. Once you close the tab, nothing is retained anywhere.

Does it work on scanned PDFs?

This tool compares the text layer of a PDF. Scanned PDFs that are images without an embedded text layer will show no text to compare. If you have a scanned PDF, first run it through our PDF OCR tool to extract the text before comparing.

What is the maximum file size?

Each PDF can be up to 50 MB. Very large documents with many pages may take a few seconds longer to process as each page is rendered individually in the browser.

Can I compare PDFs on iPhone or Android?

Yes. The tool runs entirely in the browser and works on Safari (iPhone/iPad) and Chrome (Android). Tap each upload zone to select files from your device or cloud storage.

Can I compare password-protected PDFs?

No — the tool cannot unlock password-protected PDFs. You will need to remove the password protection first (using Adobe Acrobat or a PDF unlocker tool) and then upload the files. Once the password is removed, the comparison works like any other PDF.

How accurate is the PDF text comparison?

The accuracy depends on the quality of the text layer in each PDF. Digitally created PDFs — exported from Word, Google Docs, or similar — produce highly accurate comparisons. Scanned PDFs without an embedded text layer will show no differences, as there is no text to compare. Run them through a PDF OCR tool first to extract the text before comparing.

Related Tools

Need to compare plain text instead of PDFs? Use the Text Diff Checker. Want to extract the text layer from a PDF first? Try the PDF to Text Extractor. Browse all PDF utilities on QuickTooly.