Can a website rename the files on my computer?

No. A browser lets a page read the files you choose but not rename them where they are, so this tool writes renamed copies into renamed.zip and your originals keep their names. Unzip renamed.zip wherever you want the renamed set.

How do I number files 001, 002, 003?

Set numbering to In front of the name or At the end of the name and type 001 as the start. The number of digits you type is the width, so 001 counts 001, 002, 003, and a number that outgrows the width keeps all its digits, so 999 is followed by 1000. The step sets the gap between numbers, from 1 to 1,000,000, and joined with puts an underscore, a hyphen, a space, a dot or nothing between the number and the name. Files are numbered in the order you pick: as added, by name, by date modified or by size.

Why is a new name flagged as a clash?

Windows and macOS treat Report.pdf and report.pdf as the same file, and macOS also treats an accent typed as one character (NFC) and as a letter plus a combining mark (NFD) as the same. Two such names in one ZIP land on one file when it is unzipped there, so the download waits until every name differs. Turning on numbering gives every file its own number, or you can remove one of the files.

What happens to a slash, a colon or a name like CON?

The path separators / and \ and the colon become a hyphen, the characters " | ? * become an underscore, control and text-direction characters become an underscore, invisible characters such as a zero-width space are removed, and trailing dots and spaces are dropped. Reserved Windows names, including CON, PRN, AUX, NUL, COM0 to COM9 and LPT0 to LPT9, get an underscore after them with or without an extension, so CON.txt becomes CON_.txt. A name longer than 255 bytes is cut from the part that came from the original name, so the prefix, the suffix, the number and a normal-length extension stay. Every change is listed under the new name.

Does renaming change what is inside the files?

No. Each file is stored in the ZIP byte for byte, without compression, with its last-modified date. Changing the extension changes the name only: a PNG renamed to .jpg is still a PNG inside.

How many files can I rename at once?

Up to 2,000 files and 1 GB in one ZIP, checked from the file sizes before anything is read. For a larger set, rename it in batches and start each batch's numbering where the last one ended.

Is find and replace case sensitive?

It is when Case must match is ticked, which is how the page starts; untick it to match any case. Find looks only at the name before the extension, replaces every occurrence, and treats what you type as plain text, so characters such as . * ( ) have no special meaning.

Are my files uploaded?

No. Files are read and zipped in this tab, and only the rules are remembered in this browser, never your files or the list of names.

Batch File Renamer

Rename a batch of files with numbering, find and replace, a prefix or suffix and an extension rule, check every new name beside the old one, then download the renamed copies as a ZIP. Names that would be the same file on Windows or macOS, differing only in case or in how an accent is spelled, are flagged, and the ZIP waits until they differ. Path separators, reserved Windows names such as CON, control characters, trailing dots and spaces and names over 255 bytes are rewritten, and every fix is listed under the new name. Files are read and zipped in this tab, never uploaded.

rules

no files yet

findreplaceCase must match

on the name only, never the extension; plain text, not a pattern

prefixsuffixKeep the original namenumberingstartstepjoined with

the digits you type set the width: 001 counts 001, 002, 003

extensionnew extension

changes the name only: a .png renamed .jpg is still a PNG inside

order

originals never touched: the renamed copies go into a ZIP

Add files

preview

empty

Add files to rename

Use Add files, or drop files here. Each new name shows beside the old one before anything is written, and nothing is uploaded.

Files: none

Renamed: none

Clashes: 0

Download: add files first

Files are read and zipped in this tab and never uploaded. Each renamed copy is stored in the ZIP without compression and keeps its last-modified date; unzip it wherever you want the renamed set.

One ZIP takes at most 2,000 files and 1 GB. Only the rules are remembered in this browser, never your files or the list of names.

Try an example

Small text files written for this page and marked as examples. Trying one replaces the list and the rules.

a.txt and b.txtnumbering from 001, in front, joined with _
001_a.txt and 002_b.txt
Report.PDF and report.pdfextension set to lower case, no numbering
Report.pdf and report.pdf differ only in case: flagged as a clash, and the ZIP waits until they differ
Replace IMG_ with 09/14_, and a file named CON.txta path separator and a reserved Windows name
IMG_0412.JPG becomes 09-14_0412.JPG, CON.txt becomes CON_.txt, and both fixes are listed in the report

Accuracy. Only the copies in the ZIP you download get the new names: a browser cannot rename the files on your disk, so your originals keep theirs. Clashes are checked ignoring case and Unicode form, and path separators, reserved Windows names such as CON, control characters, trailing dots and spaces and names over 255 bytes are rewritten and listed before you download. File contents are stored in the ZIP byte for byte, uncompressed.

Common questions

Can a website rename the files on my computer?: No. A browser lets a page read the files you choose but not rename them where they are, so this tool writes renamed copies into renamed.zip and your originals keep their names. Unzip renamed.zip wherever you want the renamed set.
How do I number files 001, 002, 003?: Set numbering to In front of the name or At the end of the name and type 001 as the start. The number of digits you type is the width, so 001 counts 001, 002, 003, and a number that outgrows the width keeps all its digits, so 999 is followed by 1000. The step sets the gap between numbers, from 1 to 1,000,000, and joined with puts an underscore, a hyphen, a space, a dot or nothing between the number and the name. Files are numbered in the order you pick: as added, by name, by date modified or by size.
Why is a new name flagged as a clash?: Windows and macOS treat Report.pdf and report.pdf as the same file, and macOS also treats an accent typed as one character (NFC) and as a letter plus a combining mark (NFD) as the same. Two such names in one ZIP land on one file when it is unzipped there, so the download waits until every name differs. Turning on numbering gives every file its own number, or you can remove one of the files.
What happens to a slash, a colon or a name like CON?: The path separators / and \ and the colon become a hyphen, the characters < > " | ? * become an underscore, control and text-direction characters become an underscore, invisible characters such as a zero-width space are removed, and trailing dots and spaces are dropped. Reserved Windows names, including CON, PRN, AUX, NUL, COM0 to COM9 and LPT0 to LPT9, get an underscore after them with or without an extension, so CON.txt becomes CON_.txt. A name longer than 255 bytes is cut from the part that came from the original name, so the prefix, the suffix, the number and a normal-length extension stay. Every change is listed under the new name.
Does renaming change what is inside the files?: No. Each file is stored in the ZIP byte for byte, without compression, with its last-modified date. Changing the extension changes the name only: a PNG renamed to .jpg is still a PNG inside.
How many files can I rename at once?: Up to 2,000 files and 1 GB in one ZIP, checked from the file sizes before anything is read. For a larger set, rename it in batches and start each batch's numbering where the last one ended.
Is find and replace case sensitive?: It is when Case must match is ticked, which is how the page starts; untick it to match any case. Find looks only at the name before the extension, replaces every occurrence, and treats what you type as plain text, so characters such as . * ( ) have no special meaning.
Are my files uploaded?: No. Files are read and zipped in this tab, and only the rules are remembered in this browser, never your files or the list of names.

Only the copies in the ZIP you download get the new names: a browser cannot rename the files on your disk, so your originals keep theirs. Clashes are checked ignoring case and Unicode form, and path separators, reserved Windows names such as CON, control characters, trailing dots and spaces and names over 255 bytes are rewritten and listed before you download. File contents are stored in the ZIP byte for byte, uncompressed.