Trim a ROM from the CLI

Cut the padding off a ROM with rom-weaver trim, check the saving before you commit to it, and pad a trimmed file back out again.

See what would change

-n/--dry-run reports the planned size change without writing a trimmed output:

rom-weaver trim --input game.nds --dry-run

Write a trimmed copy

rom-weaver trim --input game.nds --output game-trimmed.nds

--extension names the copy from the input instead. It cannot be combined with --output or --in-place:

rom-weaver trim --input game.nds --extension trimmed.nds

trim does not accept GameCube or Wii discs. They are detected by content in any supported disc container (.iso, .gcm, .rvz, .wbfs, .wia, .gcz, .ciso, .tgc, .nfs), whatever the extension. A lone disc, or a lone archive that holds only discs, stops with an error that names the input and points to compress; convert the disc to RVZ with rom-weaver compress --input game.iso --output game.rvz. In a folder or multi-file run, discs (including discs inside archives) are skipped, counted as unsupported and in skipped_gamecube_wii, and the run notes that rom-weaver compress writes RVZ. Other non-XISO .iso files, such as PS2 images, are skipped as unsupported.

Choose the output format

--output (and --extension) follow the output name's extension, as compress and patch apply do. A container extension packs the trimmed file inside it; a name that matches no container writes the trimmed file itself.

The file inside an archive carries the output name without the archive extension, ending in the trimmed file's own extension: --output game.zip for game.nds holds game.nds, and --output game.nds.zip holds game.nds. An existing output is kept unless you pass --force, and a failed pack leaves it as it was. --dry-run applies the same rules and reports the container as the file it would write.

--in-place rewrites the source file. Use it instead of pointing --output at a symlink or hard link to the input; output aliases are rejected even with --force. Keep a known-good copy first; a trimmed ROM is not always the file a patch expects.

A successful trim prints nothing. Add -v to list each file it wrote; warnings and errors always print.

Make the trim reversible

For NDS-family, GBA, and 3DS ROMs, write a separate copy with --revert-marker to record the original length and padding byte. XISO rejects this option because rebuilding the disc cannot be reversed from a padding footer:

rom-weaver trim --input game.gba --output game-trimmed.gba --revert-marker

--revert-marker applies only when trimming; combining it with --revert is an error. The footer stores one repeated byte, not a copy of the removed data. Exact restoration requires uniform removed padding. Keep the source when trimming NDS files whose removed area may contain other bytes. The fill byte is recorded before trimming, including with --in-place.

Put the padding back

rom-weaver trim --input game-trimmed.gba --output game.gba --revert

--revert works for NDS, GBA, and 3DS. XISO trimming does not support this operation. Without a footer from --revert-marker, the restored padding is reconstructed and may not be byte-identical.

Trim files inside an archive

trim opens archives for you and filters to ROMs by default:

rom-weaver trim --input games.zip

trim reads the archive's file list first and extracts only the members it can use: trimmable ROMs, .iso files that may be XISO discs, and nested archives (including CHD and CSO, which can hold an XISO). GameCube/Wii discs are skipped without extraction when their name gives them away (.rvz, .wbfs, .wia, .gcz, .gcm, .tgc), or by reading the first bytes of an .iso or .ciso member, which works in ZIP, 7z, RAR, tar, and single-file streams such as .iso.gz.

Nested ZIP and tar archives can be inspected without extracting them. This includes compressed tar archives such as .tar.gz. Trim skips them when they hold only discs or files it cannot use.

Duplicate member names or unverified ZIP listings fall back to extraction. ZIP64 and ZIP directories exceeding the 1 MiB inspection window also use this fallback. Other nested archives, such as 7z, are extracted first. The discs inside them are still skipped.

Each supported ROM is written beside the archive using its member filename and the trim extension. --output requires exactly one supported ROM. Conflicting output names are rejected before writing, including with --force.

--no-filter also extracts members with names that say nothing about their contents, such as bundle.dat, so their contents decide; known GameCube/Wii discs are still skipped. A patch-only --filter is rejected.

Look up what is supported

Trim support lists every trim target and every flag alias. For whether to trim at all, see Choosing a compression format.