Rename a folder of 200 files and you find out three things fast: the naming convention you half-remember, the two names that would collide, and the fact that most web-based rename tools want the whole folder before they show you a single new name.

The File Studio's Batch rename tab in OnePassApps does the opposite. You drop the files in, type the rule, and a rename preview tells you exactly what each name becomes before anything is packed.

Disclosure: I work on OnePassApps.

Open the File Studio to try it, or read the app guides for the rest of the tools.

The three steps

  • 01 Source — the files you picked. The counter starts at "0 files · 0 B." and the panel tells you what will come back: "Renamed copies are packed in one ZIP."
  • 02 New names — Prefix, Suffix before extension, Find in filename, Replace with, a Case conversion control, an "Add sequence number" checkbox and a "Starts at" field. The hint under the numbering is "Turn on numbering first."
  • 03 Result — "Create renamed copies ZIP packs the new names into renamed-copies.zip. Names on your device never change."

That last sentence is the whole design. It makes copies; it does not touch your disk. The drop area says "Up to 500 files and 256 MiB · the names on your device never change", and the page repeats the two lines this Studio is built on: "Nothing leaves this tab." and "Processing stays in this browser."

What the rename preview actually shows

The preview panel is headed RENAME PREVIEW and starts empty ("Nothing chosen yet"). Once files are loaded it lists, per file, the old name, the new name and the size.

Here is a run I did on two real files, "Q3 Report.txt" and "notes.txt", five bytes each. I typed 2026- into the Prefix field and ticked "Add sequence number". The preview read:

  • 2 files
  • 2 names change
  • Q3 Report.txt → 2026-Q3 Report-1.txt
  • notes.txt → 2026-notes-2.txt

Look at where the number lands: it is inserted before the extension, and it counts across the whole selection in order, so the second file gets 2 even though the sequence started at 1.

The collision rule

Rename rules collide. Two different files can end up with the same new name, and whatever builds the archive has to resolve that or one file silently disappears.

The panel states the rule in one line: "Name collisions are resolved in selection order with “(2)”, “(3)” and so on."

So a name that is already taken in the pack gets (2) appended, then (3), and the order comes from the order you selected the files — not from alphabetical order. Selection order is the thing to control here, because that is what decides which file keeps the clean name and which one gets the suffix.

The other two name controls

Two more controls sit in step 02, and both compose with the prefix:

  • Find in filename / Replace with — a search-and-replace applied to the name, not to the contents. Fill them in and the preview updates as you go.
  • Case conversion — a control that opens on "Keep as-is".

The preview is the only place the combined result shows, so it is worth reading every line of it before you pack anything. Two rules that each look fine on their own can produce a name you did not want.

What you get back

The action button reads "Create renamed copies ZIP", and the panel explains the promise: "Create renamed copies ZIP packs the new names into renamed-copies.zip. Names on your device never change."

One ZIP with the new names inside, and the originals still exactly where they were. Nothing was renamed in place, so if the preview is wrong you have changed nothing and there is nothing to undo.

Who this is for

If the job is "rename these 300 screenshots by date and number", this tab is quicker than a shell script and it needs no terminal. If the job is "rename the folder itself" or "rename in place", it will not do that — the tool deliberately makes copies. And if the renamed files need to go somewhere else, the ZIP is the hand-off, because there is no upload step and no server step.

The rest of the File Studio sits next to it: ZIP files, Unzip files, File hash, Find duplicates, Split file and Join parts.

Disclosure again: I work on OnePassApps, the team behind app.onepassapps.com.