Compare PDFs
Local Processing (Offline Capable)Text-level diff between two PDFs using LCS line alignment, generating side-by-side highlighted HTML reports and Redline PDFs. Runs locally in your browser — your file is never uploaded.
How this tool works (no sign-up needed)
- Upload your file above. Each tool shows whether it runs Local (in your browser) or Cloud (encrypted servers).
- Adjust options, then click the Run / Convert / Process button.
- Wait for progress, then download the result. Use Next tools to continue.
If buttons are not visible, enable JavaScript — the interactive workspace loads in your browser.
Free · LocalText-level diff between two PDFs, side-by-side HTML report
Supports application/pdf
Select exactly 2 PDFs (original first, revised second).
Local — your file is processed in your browser and not uploaded to us. No account needed.
What is it?Compare PDFs is a PDFLean smart document tool: Text-level diff between two PDFs using LCS line alignment to generate side-by-side HTML reports and Redline PDFs locally without uploading files.
TL;DR: Text-level diff between two PDFs using LCS line alignment, generating side-by-side HTML reports and Redline PDFs. Everything runs locally in your browser — your file is never uploaded and is cleared upon closing the page; text-layer comparison only (recommended ≤ 10MB per file).
About this tool
Text-level comparison between two PDFs using LCS line alignment. Generates side-by-side HTML diff reports and Redline annotated PDFs with change statistics. Everything runs locally in your browser's memory — free, no account required, and files never leave your device (handles files, recommended ≤ 10MB per file for smooth processing).
How to use
Upload the original and revised PDF documents
Click "Compare PDFs" to run local text extraction and LCS line alignment
Review change statistics and side-by-side highlighted differences
Download the standalone HTML report or export a Redline annotated PDF
FAQ
Will my file be uploaded?
No. Everything runs locally in your browser — text extraction and algorithmic diffing run entirely in client memory; your files are never uploaded and are cleared upon closing the page.
Are there any limits?
This is a text-level comparison (it does not compare visual pixels or layout). It requires exactly two files (≤ 10MB recommended). Scanned PDFs without a text layer must be processed with OCR first.
How does the comparison algorithm work, and what if paragraph order changes?
Comparison extracts the PDF text layer and applies LCS line alignment. If content order changes, it is reported as deletions from the old position and additions at the new position. Scanned PDFs require OCR first.
Can I process multiple files in bulk?
A single tool page handles one task at a time; for bulk work use the Batch Processing workflow and add this tool as a step to run a whole set at once.
Is the processed file still editable?
The outputs are a standalone dual-column HTML comparison report and a Redline annotated PDF (added lines highlighted in place, deleted lines appended at the end); original files remain unchanged.