How to Keep Metadata and Album Art When Converting Audio

By the M4AtoMP3.org editorial team · October 21, 2026 · 10 min read

You convert an album from M4A to MP3, copy it to your phone or car, and every track shows up as Unknown Artist – Track 01 with a grey music-note icon. The audio is fine; the metadata didn’t survive the trip. This happens because M4A and MP3 store tags in completely different ways, and many converters translate only some of them. This guide explains why, how to convert so tags and artwork come through, and how to repair files that have already lost them.

How each format stores tags

M4A uses the MPEG-4 container’s metadata atoms, the same system iTunes uses. Each field (title ©nam, artist ©ART, album ©alb, track number trkn, cover art covr …) is a separate item in the file. Cover art is stored as an image inside a metadata atom.

MP3 has no built-in metadata. Tags were added later as ID3:

• ID3v1 — a fixed 128-byte block at the end of the file, limited to 30 characters per field and no artwork. Obsolete, but still read by very old devices.
• ID3v2.3 (1999) — at the start of the file, supports long text, Unicode (UTF-16), artwork and many fields. The most widely supported version.
• ID3v2.4 (2000) — adds UTF-8 and some refinements. Better on paper, but Windows File Explorer, Windows Media Player and many car stereos don’t read it properly.

Converting means translating each M4A atom into an ID3 frame. If the converter maps only a few common fields, or writes v2.4, or drops the picture, you lose information.

What usually goes missing — and why

That last one is surprisingly common: iTunes and the Music app can store downloaded artwork in their own database rather than inside each file, so there’s nothing to copy.

Converting with tags intact

ffmpeg

The most complete one-liner:

ffmpeg -i in.m4a -map 0:a -map 0:v? -map_metadata 0 -c:a libmp3lame -q:a 2 -c:v copy -id3v2_version 3 -write_id3v1 1 out.mp3

• -map_metadata 0 copies all global tags from the input.
• -map 0:v? includes the cover picture if it exists.
• -c:v copy keeps the image as is.
• -id3v2_version 3 writes the compatible tag version.
• -write_id3v1 1 adds a basic ID3v1 tag for old devices.

See converting with ffmpeg for batch loops that use this command.

Apple Music / iTunes

Create MP3 Version copies the standard fields and embedded art. If Windows or a car stereo doesn’t show the tags, select the MP3s in iTunes and choose File › Convert › Convert ID3 Tags…, then pick v2.3.

foobar2000

Its converter copies tags and embedded art and lets you choose ID3v2.3 under the converter’s Other › ID3v2 writer compatibility mode setting.

Browser converters

Our M4A to MP3 converter copies the text tags (title, artist, album and so on) and writes ID3v2.3 for compatibility. It does not currently carry over embedded cover art, so if artwork matters, add it afterwards with a tag editor as described below — a batch of albums takes a couple of minutes in Mp3tag.

Fixing tags after conversion

Mp3tag (Windows, macOS)

The standard tool for batch tag editing.

1. Open the folder of MP3s (File › Change directory).
2. Select files and edit fields in the left panel; changes apply to all selected files.
3. Add cover art: select an album’s tracks, right-click the cover box › Add cover, choose a JPEG and save. To use art already in the folder (cover.jpg), use an action with Import cover from file.
4. Fill tags from file names: Convert › Filename – Tag with a pattern like %track% - %artist% - %title%.
5. Copy tags from the M4A originals: open both sets, select the M4As, Edit › Copy tag, select the MP3s in the same order, Edit › Paste tag.
6. Under Tools › Options › Tags › Mpeg, set Write ID3v2.3 UTF-16 for maximum compatibility.

Kid3 (Windows, macOS, Linux)

A good cross-platform alternative with similar batch features, including importing tags from MusicBrainz and Discogs.

MusicBrainz Picard

Identifies tracks by acoustic fingerprint and fills in complete, consistent tags and cover art. Ideal when the originals had poor tags anyway.

Command line

eyeD3 (Python) or id3v2 can set tags in scripts. With ffmpeg you can add a cover to an existing MP3 without re-encoding:

ffmpeg -i song.mp3 -i cover.jpg -map 0:a -map 1 -c copy -id3v2_version 3 -metadata:s:v title="Album cover" -metadata:s:v comment="Cover (front)" song-with-art.mp3

Cover art that works everywhere

• Format: JPEG (PNG works on most modern devices, but JPEG is safest).
• Size: 500 × 500 to 1000 × 1000 pixels. Some cars and older players fail on art above about 1000 px or several hundred KB.
• Type: mark it as Front cover — some devices ignore other picture types.
• One image per file: multiple embedded images can confuse simple players.
• Avoid progressive JPEGs for older hardware; save as baseline.

Track numbers and sorting

Players sort albums by track number, not file name. Make sure each MP3 has a track number (1, 2 … or 1/12) and a disc number for multi-disc albums. For compilations, set Album Artist to “Various Artists” so the album isn’t split into one entry per artist. Car stereos and older players often sort by file name instead, so it’s worth naming files with a leading zero-padded track number (01 - Title.mp3).

Voice memos and recordings

Voice memos rarely have useful tags — the “title” is often just the location or “New Recording”. Before sharing a batch of converted recordings, it is worth setting:

• Title: a descriptive name (e.g. Team meeting – budget review).
• Artist: the speaker, or your name.
• Album: the project or course name, so the files group together.
• Date/Year: the recording date.

That turns a folder of anonymous files into something you can search and browse.

Checking what’s actually in a file

• ffprobe: ffprobe -hide_banner out.mp3 prints the ID3 tags and shows the attached picture as a video stream.
• Mp3tag: the Tag column shows the versions present (e.g. ID3v2.3, ID3v1).
• Windows: right-click › Properties › Details. If fields are blank here but appear in other apps, the file probably uses ID3v2.4.
• Mac: Get Info in Finder or the Music app.

Lyrics, ratings and play counts

Some information lives in the file, some only in your player’s database:

• Lyrics stored in an M4A map to the ID3 USLT frame. ffmpeg copies them with -map_metadata 0 in most builds; check with a tag editor.
• Star ratings and play counts are stored in the Music app or iTunes library, not in the file, so they never transfer through conversion. Tools exist to write ratings into ID3 POPM frames, but few players read them.

Summary

Tags are lost during conversion because M4A atoms have to be translated into ID3 frames, and many tools translate only part of them. Use a converter that copies metadata and art and writes ID3v2.3, keep cover images to about 1000 px JPEG, and use Mp3tag, Kid3 or Picard to fill any gaps afterwards. Your library — and your car stereo — will thank you.

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