Bulk Renamer

Knowledge Base

What It Actually Does

Pick a folder, and every file in it (not subfolders) loads into a preview list. Configure a rename pattern, find/replace, an added prefix or suffix, sequential numbering, case conversion, or an extension change, and the preview table updates live showing exactly what every file's new name will be, before anything happens on disk.

The Safety Model

Two checks run before any file is renamed: no two files may end up with the same new name, and no destination name may already exist on disk (a same-file case-only rename is allowed). If either check fails, nothing is renamed and the conflicting rows are highlighted so you can fix the pattern. A single "Undo Last Rename" button reverses the most recent successful batch, as an immediate safety net. It's in-memory only and won't survive closing the app.

Pattern Options

Find & replace (plain text or regex), prefix/suffix, sequential numbering with configurable start number and zero-padding, case conversion (lowercase, UPPERCASE, Title Case), and an optional extension change, combine as many as you need in one pass.

FAQ

Q: Is this actually free?
A: Yes, free and open-source under the MIT license. No account, no trial, no watermark.

Q: Can it undo a rename if I make a mistake?
A: Yes, for the most recent batch. An Undo button reverses the last rename it applied. This is an in-memory safety net for catching an immediate mistake, not a permanent history, so it won't help after closing the app.

Q: Will I get a security warning when I open it?
A: Possibly, until code-signing is set up for this project, unsigned apps trigger a standard OS warning on first launch (Gatekeeper on macOS, SmartScreen on Windows). The app itself is unaffected. You can review the source on GitHub before running it if you'd like to verify that yourself.

Naming files so they stay findable

A naming convention is a decision made once that pays out every time somebody opens the folder. The requirements are modest: names should sort correctly, describe their contents without being opened, and survive being moved between systems. Almost every convention failing in practice fails one of those three.

Dates belong at the front and belong reversed. Writing 2026-08-19 sorts chronologically by default in every file browser, while 19-08-2026 sorts by day of the month across every year at once, which is never useful. This one habit does more for a media archive than any other naming decision.

Pad your numbers. A folder containing take 9 and take 10 sorts them as 10 before 9, because sorting compares characters rather than values. Writing 009 and 010 fixes it permanently, and choosing three digits rather than two costs nothing at the point where a project unexpectedly reaches its hundredth file.

Keep names conservative. Spaces cause problems in command line tools and web addresses, and slashes, colons and question marks are outright illegal on at least one major operating system. Hyphens and underscores work everywhere. Very long paths also fail on some systems, so deeply nested folders with descriptive names at every level eventually hit a limit.

Always preview before applying. A rename running across four hundred files with a pattern error produces four hundred wrong names and no record of the originals. Reading the preview takes seconds, and reconstructing names from memory takes an afternoon and is usually incomplete.

Vocabulary

Naming convention. An agreed pattern for constructing file names so that everybody on a project produces consistent, sortable results. Its value comes entirely from being followed consistently rather than from being clever.

Zero padding. Writing numbers with leading zeros, such as 007 instead of 7, so they sort in numerical order. Necessary because file browsers compare names character by character rather than understanding numbers.

ISO date format. Writing dates as year, then month, then day, as in 2026-08-19. Sorts chronologically without any special handling and removes the ambiguity between day-first and month-first conventions.

Batch operation. An action applied to many files at once. Fast and unforgiving, since a mistake in the pattern applies to everything, which is why previewing before committing matters more here than in single-file work.