Bulk File Rename

About the bulk rename tool

DSC_0041.JPG, DSC_0042.JPG, IMG-20240611-WA0002.jpg — a folder of photos straight off a camera and a phone is unreadable, and renaming them one at a time is nobody's idea of an afternoon. This tool renames the whole folder in one go: set the rules, check the before-and-after preview, then apply it or take a script.

It handles the things people actually need — find and replace, sequential numbering, prefixes and suffixes, letter case, spaces, dates from the file itself, and changing the extension — and it checks for name collisions before anything happens, which is the part that makes bulk renaming risky when you do it by hand.

The folder is read inside your browser. Nothing is uploaded.

How to use it

• Click Choose a folder and pick the one you want to rename
• Set your rules. The preview updates as you type, showing every before → after pair
• Check the warnings. Any collision is highlighted, and renaming stays blocked until none are left
• Apply it — download a script and run it yourself, or use Rename now if your browser supports it

The rules, and the order they run in

Rules are applied in a fixed order, so the result is predictable rather than depending on which box you filled in last:

• Find and replace — on the name only, never on the extension, so .jpg cannot be mangled by accident. Tick Find is a regular expression for patterns, or leave it off for plain text
• Spaces — replace with -, replace with _, or remove them
• Letter case — lower, UPPER or Title Case
• Name pattern — replaces the name outright. See below
• Prefix and suffix — wrapped around whatever the name became
• Change extension — applied last

The name pattern

The pattern field builds a new name out of pieces:

• {name} — the name so far, after find-and-replace, spaces and case have been applied
• {n} — a sequential number. Numbering starts at sets the first value, Digits pads it, so 3 digits gives 001, 002, 003
• {ext} — the original extension
• {date} — the file's own modified date as 2024-06-11
• {year}, {month}, {day} — the same date in parts

So Holiday-{n} on four photos gives Holiday-001.jpg through Holiday-004.jpg. {year}-{month}-{name} gives 2024-06-DSC_0041.jpg. Leave the pattern blank and the original name flows through the other rules untouched.

Numbering order decides which file gets number 1 — by name, by date, by size or by path. Sorting by date is what you want for photos, so the sequence follows the order they were taken rather than whatever the camera called them.

When Include subfolders is on, numbering restarts in each folder. A single sequence running 1 to 500 across unrelated subfolders would be meaningless, and would risk collisions.

Collisions, and why renaming is blocked

Two rules of thumb break bulk renames: two files ending up with the same new name, and a new name that is already taken by a file you are not renaming. Both are caught before anything happens and shown in the preview:

• two files would get this name — your rules are not specific enough. Adding {n} usually fixes it
• a file with this name is already there — the target name exists in that folder and is not itself being renamed away
• the new name would be empty — the rules stripped everything

While any of these stand, both Rename now and the script download are disabled — a script that quietly renamed the half that did not collide would be worse than one that refuses. Fix the rule, the warning clears, and both come back. Rows that would not change at all are shown greyed and simply skipped.

Two ways to apply it

Download a rename script is the default and works in every browser. You get a .bat for Windows or a .sh for Mac and Linux, containing one rename per line with everything properly quoted, which you run from inside the folder. Nothing happens until you run it, and you can read the whole thing first.

Rename now appears only in browsers that can rename files directly — currently Chrome, Edge and Opera. It asks separately for permission to edit the folder, which is a different and stronger prompt than the read permission you gave when picking it. Files are renamed one at a time and the preview updates as it goes; if any single rename fails, the rest still run and the count of failures is reported.

What people use it for

• Turning camera filenames into something readable, numbered in the order the photos were taken
• Adding a project code or client name as a prefix across a delivery folder
• Stripping junk like -copy, (1) or _final_FINAL out of a working folder
• Making filenames web-safe — lower case, no spaces — before uploading them
• Prefixing files with their own date so they sort chronologically anywhere
• Fixing the extension on a batch of files saved with the wrong one

Good to know

• Nothing is uploaded. The folder is read in the page and, if you use Rename now, written in the page too
• Characters Windows forbids in a filename — \ / : * ? " < > | — are stripped from the new name automatically, so a rule cannot produce an unusable name
• An unfinished regular expression does not blank the preview; it is simply ignored until it is valid
• The preview lists the first 500 files. A larger folder still renames in full, and the script contains every line
• Firefox and Safari can preview and download the script but cannot rename in the page, because their folder upload gives no handle to rename through
• Very large folders are capped at 200,000 items so the page cannot freeze

Related tools

• Folder & File List — list a folder before and after renaming
• Duplicate File Finder — find identical files in a folder
• Compare Two Folders — check a rename went the way you expected
• Find and Replace — the same idea on a piece of text