Learn RenForge by example.

Your first rename

Goal: turn camera names into holiday names. The folder contains IMG_0042.JPG, IMG_0043.JPG, IMG_0044.JPG and a few .txt notes you want to leave alone.

1. Click Select Folder… (or drag the folder onto the window).
2. Under 1. Filters, click + Add filter, choose extension and type jpg. Only the photos remain in the list.
3. Under 2. Rename steps, click + Add rename step. Choose Replace text: find IMG_, replace with Holiday_.
4. Add a second step, Change case → lowercase extension.
5. Check the preview. Untick any file you want to skip.
6. Click Apply with Dry run ticked (the default). RenForge only reports what it would do.
7. Happy? Untick Dry run and click Apply again. Keep Create undo log ticked.

The window

Filters

Filters decide which files appear in the preview. With no filters every file in the folder is included. A filter with an empty value is ignored, and only the file name is checked, never the folder path.

• Match ALL (AND): a file must satisfy every filter. Match ANY (OR): at least one.
• Case sensitive is off by default, so PNG and png are the same.
• An invalid regular expression is flagged in red and matches nothing.

Selecting & sorting

• Every matching file has a checkbox. Untick files to leave them alone. Select All / Deselect All act on the files currently listed.
• Show: All / Changed / Problems narrows the preview. Changed hides unchanged and unticked files; Problems shows only files with a ⚠ (invalid name, duplicate name, or a name already taken by a file that is not being renamed). The buttons show live counts, and Problems turns amber when something needs fixing.
• The header shows the counts, for example 42 matches · 38 selected · 100 total files.
• The list scrolls smoothly even with tens of thousands of files, and folders are scanned in the background.
• Order sorts by name (natural: img2 before img10), date (capture date, else modified) or size. Numbering follows the order shown.
• Rows marked (unchanged) already have the target name and are skipped.

Rename steps

Steps form a pipeline: the result of step 1 is the input of step 2, and so on. Use ▲ ▼ to reorder, the checkbox to switch a step off without deleting it, and ✕ to remove it. Order matters: Prepend then Change case is not the same as the reverse. Each step shows an Example line (the first selected file, before → after that step), and the arrow button collapses a step to one line.

Replace text & Remove text

Replace swaps every occurrence of A for B (leave B empty to delete). Remove deletes the text. Matching is case sensitive.

Prepend, Append & Insert before extension

Change extension

With or without the dot; empty removes the extension. .tar.gz, .tar.bz2, .tar.xz and .tar.zst count as one extension, and dotfiles such as .bashrc have none.

Change case

Changes the case of the name; the extension is untouched unless you pick an extension option.

Clean up

Numbering

Number files gives every selected file a sequence number, in the order shown. Untick a file and the others are renumbered.

• A (template): {n} = number, {n:3} = padded to 3 digits, {name} = original name without extension. The extension is kept automatically. Empty means {name}_{n:3}.
• B (start, step): 1 starts at 1; 100,10 gives 100, 110, 120…
• Tick Restart numbering in each folder when Include subfolders is on and each folder should start again.

Regex

A regular expression (regex) describes a pattern. In Regex replace, A is the pattern and B the replacement; $1, $2… insert the parts captured by brackets. The whole name, extension included, is matched. Start the pattern with (?i) to ignore case. The regex filter uses the same syntax and follows the Case sensitive box. The syntax is Go's RE2.

Tip: follow a regex that leaves double spaces with Clean up → Collapse repeated spaces.

Photos & EXIF dates

Rename from template builds the whole name from tokens. The capture date is read from the EXIF data inside the picture (JPEG and TIFF-based RAW formats such as CR2, NEF, DNG, ARW). Files without EXIF (and HEIC/CR3, whose metadata RenForge cannot read yet) use their modified date, so the template still works. EXIF is only read, never written.

Related files (XMP, JPG pairs)

Under 3. Options, tick Also rename related files. For every file that gets a new base name, RenForge also renames files next to it that have the same base name and another extension from your list (default xmp, aae, dop, pp3, jpg, jpeg, tif, tiff, png, heic, cr2, cr3, nef, arw, dng, raf, orf, rw2, mov, thm), or are Adobe-style sidecars of the full name (IMG_001.CR2.xmp).

• The preview shows (+3 related) on the main file.
• A group is all or nothing: if any member would conflict, none of that group is renamed.
• Changing only the extension leaves related files alone.
• Related files come from the folders that were scanned; tick Include subfolders if they live deeper.

Image sequences

Shift frame numbers adds an offset to the number at the end of the name. A is the offset (+1000, -1), B an optional padding (empty keeps the current width). Only the last number changes.

Shifts such as +1 are fine: RenForge moves all files out of the way first. If a file that is not part of the batch occupies a target, the whole affected chain is skipped and reported, so nothing is half-shifted. Undo restores such shifts too. A frame that would become negative is left unchanged.

Presets

Click Presets… (next to + Add rename step):

• Load a built-in or your own preset. Loading replaces the current filters and steps.
• Save current as… stores your filters, steps and match options under a name (saving under an existing name asks before replacing it).
• Delete removes your own presets; built-ins cannot be deleted.

Your presets are plain JSON files in renforge/presets inside your user configuration folder (macOS ~/Library/Application Support, Windows %AppData%, Linux ~/.config). Copy them to another computer to share them.

Dry run & safety checks

When you click Apply, RenForge checks every selected file and skips any that would cause trouble. Dry run is ticked by default and changes nothing.

Allowed: swapping names (a.txt ↔ b.txt), and changing only the letter case (IMG.jpg → img.jpg), even on Windows and macOS where names are case-insensitive.

How it renames: each file first moves to a temporary name (.renforge_tmp_…), then to its final name. Existing files are never overwritten. If a file cannot be renamed it goes back to its old name; in the very unlikely case that fails too, the result dialog lists the file left under its temporary name.

Undo

Keep Create undo log (CSV) ticked. RenForge asks where to save the log (it suggests the folder you are working in) and writes it after the rename, so it records what really happened.

1. Click Undo…. RenForge offers the most recent log, or lets you choose any log file.
2. It shows how many renames can be restored and lists any it cannot: not found (moved or deleted since) or in use again (another file now has the original name).
3. Confirm, and the original names come back.

A log from a dry run contains no completed renames, so there is nothing to undo. The CSV has the columns old_path, new_path, old_name, new_name, status, reason and opens in any spreadsheet.

Recipes

Troubleshooting

Still stuck? Report a bug with your OS, the build you used, and the steps to reproduce.

Build from source

Prerequisites

• Go: the version listed in go.mod (or newer) from go.dev/dl.
• A C compiler and graphics libraries, because the UI toolkit (Fyne) needs them:
  • macOS: Xcode command line tools: xcode-select --install
  • Windows: MinGW-w64 gcc, for example via MSYS2
  • Linux (Debian/Ubuntu): sudo apt install gcc pkg-config libgl1-mesa-dev xorg-dev libasound2-dev

Run, test and build

# get the code
$ git clone https://github.com/blackarck/renforge.git
$ cd renforge

# run the app
$ go run .

# run the tests (the rename engine is UI-free and well covered)
$ go test ./...

# build a plain binary
$ go build -o renforge .

A plain go build has no application icon, and on Windows it opens a console window. For a proper app, use the Fyne packager; it reads FyneApp.toml and icon.png:

$ go install fyne.io/tools/cmd/fyne@latest
$ fyne package -os darwin     # renforge.app
$ fyne package -os windows    # renforge.exe, no console window
$ fyne package -os linux      # renforge.tar.xz

Project layout

Want to help? Read CONTRIBUTING.md or jump to how to support the project.