Bulk File Renamer Preview
Drop files and preview a batch rename — pattern with {n}, {name}, {ext}, {date}, plus find/replace, case modes, and collision detection.
How to use
- Drop or pick files. The list populates with their current names.
- Pick a preset or write your own pattern with
{name},{n},{ext},{date}. - Copy the old→new table as TSV to feed
mv, PowerShell, or your file manager's batch rename.
About this tool
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Drop in a folder's worth of files and see exactly what the rename would produce, without a single file being touched. Patterns use placeholders — {n} for a sequence number with zero-padding, {name} for the original base, {ext} for the extension, {date} from each file's last-modified timestamp — on top of a find-and-replace pass and three case modes. Rows whose new name collides with another turn red, so you see the conflict before you act on the list.
The preview is the whole product, and that is a deliberate limitation rather than a missing feature. A web page cannot rename files on your disk; it reads names, sizes and timestamps through the File API and nothing more. What you take away is a list to paste into a shell script, a rename utility or a file manager's batch tool. Nothing is uploaded and no request is made, which is why you can safely preview a folder of documents you would not put through a hosted service.
Collisions are worth the red highlighting because of what happens without it. A rename that produces two identical names does not fail on most systems; the second one overwrites the first and the file is gone with no prompt. Worse, a sequence can collide with itself midway: renaming 1.jpg to 2.jpg and then 2.jpg to 3.jpg destroys the original 2.jpg before it is ever read. The detector here catches duplicate outputs, but a rename into names that already exist in the folder is a conflict only your file system will discover, so check the destination too.
Two details about the inputs. {date} reads the file's last-modified time, which is not the date the photo was taken or the document was written — copying files from a camera or a backup usually rewrites it to the moment of the copy, so a folder that all shows today's date has been moved rather than created today. And the order files arrive in is not guaranteed to match what you saw in your file manager, which matters when {n} is numbering them: sort explicitly rather than trusting the drop order, and remember that plain alphabetical sorting puts file10 before file2.
Frequently asked questions
Does it actually rename my files?
No. Browsers can't write back to your filesystem from a regular page — this is a preview tool. Copy the table and apply it with mv, pwsh Rename-Item, or your file manager.
Where does {date} come from?
Each file's lastModified field as the browser sees it (YYYYMMDD). For uploaded files this is the OS-reported modification time, not when you uploaded them.
Two files ended up with the same new name. What happens then?
The preview flags the collision rather than letting one file quietly overwrite the other, which is what a real rename would do on most systems. Collisions usually come from a pattern that drops the distinguishing part of the name — replacing {name} with a fixed string, or numbering with too few digits when a sort puts equal names next to each other. Add {n} or keep part of the original name.
Why does case-only renaming behave oddly on Windows and macOS?
Because their default filesystems treat names as case-insensitive: to them Report.txt and report.txt are the same file, so a rename that changes only capitalisation can be refused or silently ignored, while the same rename on Linux is an ordinary move. The usual workaround is two steps, through a temporary name, and it is worth knowing before a batch of case changes goes to a shared drive.
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