Folder Difference Reviewer
Align files by relative path in two folders, then stream the actual bytes through SHA-256. A same-sized file with different content is modified. Entries only on the right are added; entries only on the left are removed. Read failures and, where supported, empty folders remain visible. The app never edits your files or performs a sync.
Key features
- Align relative paths from two actual folder selections and classify changes
- Hash bytes in 256 KiB chunks, catching same-size content changes
- Keep read/enumeration failures and normalized-name collisions explicitly indeterminate
- Use a read-only directory picker to include empty directories where the browser supports it
- Filter by folder, status or path and download the full JSON comparison manifest
How to use
- Choose the before folder on the left and the after folder on the right. Use the read-only directory picker where available, or the folder-file input as a fallback.
- Check both selection summaries and start comparison.
- Review added, removed, modified, identical and read-error counts, then filter paths and inspect sizes/hashes.
- Download the comparison manifest JSON to review paths, hashes and completeness. This tool never deletes files automatically.
Use cases
- Find actual changes between a backup and a working folder
- Spot a same-size configuration file whose bytes changed
- Separate inaccessible paths that need a later retry
- Review a manual sync plan including empty directories
Frequently asked questions
Will it delete files or synchronize the folders?
No. It only reads selected files to produce hashes and a comparison report. Added/removed describes differences from left to right; these are not automatic action commands.
What if the name and size match but content differs?
Both files are hashed from their actual bytes using SHA-256. Matching relative paths and sizes with different hashes are marked modified.
Can it see empty folders?
The read-only directory picker can enumerate empty directories in supported browsers. The folder-file input supplies files only, so it cannot establish that an empty directory exists. The report records the selection mode.
What happens when permission or reading fails?
Read and enumeration failures are marked indeterminate, and descendants of an unreadable folder are not falsely called added or removed. A report with complete=false cannot settle every path.
How are case and Unicode names compared?
Relative paths are normalized to Unicode NFC, while letter case stays significant. Names colliding after NFC normalization are reported as read errors rather than silently overwritten. Absolute, parent and empty segments are rejected.
What are the size and privacy limits?
Each side supports up to 1,000 files and 1,000 directories, 128 MiB per file and 512 MiB total. Files are read in 256 KiB chunks and their contents are never sent to this tool's server. The browser controls its own folder chooser.
Privacy
Selected files are read and hashed only in this browser. This tool neither uploads their contents nor modifies or deletes them. Downloaded JSON contains paths, sizes and hashes, so inspect it before sharing.
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