DiffMate's document comparison tool instantly identifies every difference between two files. It supports TXT, CSV, XLSX, and PDF formats, using a sequence matching algorithm based on Python's difflib SequenceMatcher to precisely highlight additions, deletions, modifications, and moves at both the line level and character level.

All processing happens entirely within your browser — no files are ever sent to an external server. Large files (up to 68 MB with over 1 million rows) are processed by a Web Worker engine running in the background, keeping the UI fully responsive during comparison. Virtual scrolling technology lets you smoothly navigate results with hundreds of thousands of lines.

Select or drag and drop two files below to compare them. Once the comparison is complete, you can review differences in a Beyond Compare-style side-by-side view, selectively merge changes between files, and download the modified result.