A tag editor you can point at ten thousand files
Mp3tag is the tool most people mean when they say tag editor, and there's no Linux build of it. rox has a full editor inside it, and a write path built for the case where a batch is large enough that "it usually works" isn't good enough.
Start with what this isn't
rox is a music player that contains a serious tag editor. Mp3tag is a dedicated tagger, and at being a dedicated tagger it's better: scripting and actions, format strings, filename-to-tag and tag-to-filename conversion by pattern, and twenty years of accumulated sharp edges filed off. If what you want is a standalone tool to run over a folder and then close, on Windows, that's the one.
The case for doing it in rox is that tagging a library is not usually a task you finish. It's something you do while you're listening, to the file you just noticed was wrong, which means the editor being attached to the player and the library is the point rather than a compromise.
The write path
This is the part worth reading even if you never install rox. Most tag writers modify your file in place: they open the original, rewrite the metadata region, and hope. That is fine tens of thousands of times and catastrophic once, because a crash, a full disk or a yanked drive partway through leaves a file that no longer parses, with your audio inside it.
rox never writes into an original. Every edit copies the file, applies the change to the copy, verifies the result by reading the metadata back and hashing the audio stream to confirm it's byte-identical to what went in, and only then atomically renames the copy over the original. If any step fails the copy is unlinked and your file is untouched, because it was never opened for writing in the first place.
Each file is also isolated, so one pathological file in a batch of four thousand fails on its own instead of taking the run down with it.
Editing a batch without flattening it
Select any number of tracks and the editor opens as one shared form. A field every file agrees on shows its value; fields that disagree show empty under a "multiple values" placeholder. Only fields you actually move write anything, so an untouched field never rewrites a file, and the ones that would be nonsense to stamp across a selection, title and track number and disc number, lock themselves in a batch.
When one file inside the batch is wrong, the form swaps for a table: one row per track, a column per field, the locked per-track fields editable in place. That's the view for the import where every title and number is differently wrong, and it beats stepping into fields one at a time. Both views commit as a single batch through the same write path, and the result lands in the library without a rescan.
What it reads and writes
- Formats. ID3v2, Vorbis comments, MP4 atoms and APE behind one editor, so MP3, FLAC, M4A and the rest are the same screen.
- Ratings. Written into the files themselves through FMPS and POPM, not into a database you can't take with you.
- Multi-value genres. Real lists, with merges kept as a library opinion rather than a rewrite of your tags.
- Cover art. Multi-picture album art, added and replaced through the same atomic path.
- Lookup. Tags and covers from MusicBrainz, iTunes and Deezer, applied through the same diff so you see what changes before it writes.
- Repair. A pass for files whose tags are damaged in specific known ways rather than merely wrong, the ones that make other taggers show a track as a filename and a zero duration.
Who should stay with Mp3tag
If you're on Windows and you lean on actions, scripting or format-string conversions, rox has no equivalent and this would be a downgrade. If you want a tagger that isn't also a player, this is the wrong shape entirely. And if your workflow is renaming files from tags in bulk by pattern, that's Mp3tag's home ground.
If you're on Linux or a Mac, or your tagging happens in the middle of listening rather than as a separate chore, that's the gap this fills.
The write path is the part that doesn't have a counterpart to compare against. Verifying an audio-stream hash before renaming over an original is not something a tagger does unless it expects to be pointed at everything you own. If that's the kind of caution you want between an edit and your files, that's what this is.
Point it at the folder you've been avoiding
Free and open source, no account, no installer. The library side of it is written up separately, and if you're coming off a Windows setup there's a MusicBee and a Foobar2000 comparison too.