About this tool
This tool compares two directory trees the way diff -r or a folder-sync utility does, but entirely in your browser. Files are matched by their path inside each folder (the top-level folder name is ignored, so you can compare release-1/ against release-2/). Each file is classified as added (only in the second folder), removed (only in the first), changed (present in both but different) or identical. Change detection compares file size first and then, for same-size files, the actual bytes, streamed in 4 MB chunks and stopping at the first difference, so it is exact (a file is only "identical" if every byte matches) and stays fast and memory-safe even on multi-gigabyte files. For changed text files, click to open a full line-and-word diff below the list. The results list is virtualized, so it stays smooth even with tens of thousands of files. Use it to review a code release, verify a backup or migration copied everything correctly, audit a config directory between environments, or confirm which assets changed in a deploy. Nothing is uploaded: hashing, comparison and diffing all run locally.
Frequently asked questions
How are files matched between the two folders?
By their relative path within each folder, with the top-level folder name stripped. So v1/src/app.js and v2/src/app.js are matched as src/app.js. Drop loose files (not in a folder) and they match by filename.
What counts as "changed" versus "identical"?
Files with different sizes are changed. Files with the same size are compared byte-for-byte, read in 4 MB chunks and stopping at the first difference, so it is exact yet memory-safe even for very large files. A file is "identical" only if every byte matches.
Can I see what changed inside a file?
Yes, click any changed text file to open a side-by-side line-and-word diff in a panel below the list. Binary files (images, archives, executables) are flagged as changed but not shown as text.
How many files can it handle?
The results list is virtualized (only the rows in view are rendered), so it stays responsive with tens of thousands of files. Reading and comparison happen on demand, so total folder size is limited only by your browser's memory, not by the tool.
Are my files uploaded?
No. Folder reading, hashing and diffing happen entirely in your browser. This works even for source trees, backups and config directories with sensitive contents.
Which browsers support folder selection?
Folder picking and folder drag-and-drop work in Chrome, Edge, Safari and Firefox. If folder drop isn't available, use the "Choose a folder" button.