Bulk File Renamer

No. The browser can't directly rename files on disk for security reasons. Instead, this tool reads the files and produces renamed copies in a downloaded ZIP. Your originals are untouched. To rename in place, you'd need a desktop tool (Windows Renamer, Bulk Rename Utility, mv on Linux/Mac, PowerShell) — but the mapping output from this tool feeds directly into those.

Pick a starting number, padding width (3 = 001, 002, ... or 4 = 0001, 0002, ...), and step (usually 1). Files are numbered in their listed order — drag to reorder before downloading. For non-sequential numbering (skip every other, custom starting point), you can adjust step or starting number.

If you've only downloaded the ZIP, yes — your originals are untouched. If you've replaced your files with the ZIP contents, you'd need to keep a backup of the originals to undo. The Copy mapping output documents the old→new mapping so you can write a reverse script if needed.

By default, extensions are preserved through all rename operations (the rules apply to the basename only). Disable that toggle to apply rules to the entire filename including extension if needed (rare, but useful for changing all .jpeg → .jpg, etc.).

Yes — JavaScript handles Unicode strings natively. Files with accented characters, CJK names, or emoji rename correctly. The downloaded ZIP preserves Unicode names; some older OS file systems may transliterate or replace unsupported characters on extraction.

No. Reading and renaming happens entirely in your browser. Sensitive filenames (project codes, client names, internal product names) stay on your device. The downloaded ZIP is created locally.