Add your AAC file
Drop one or more .aac files onto the converter above, or browse for them. They load into browser memory only — nothing is uploaded, so there is no size-based pricing and no server queue.
AAC to M4A
Re-encoding .aac audio as .m4a changes how the sound is compressed and which players will accept it. Free, private, and validated — the file never leaves your browser.
100% private for supported formats
Runs on your deviceConvert supported files
Drop AAC files here
Batch files can each use a different output. Nothing uploads for local conversions.
Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.About converting AAC audio to MPEG-4 audio
Re-encoding .aac audio as .m4a changes how the sound is compressed and which players will accept it. An .aac file holds raw Advanced Audio Coding data, usually as an ADTS stream. AAC was designed as MP3's successor and delivers audibly better quality at the same bitrate, though the bare .aac extension is rarer than AAC audio traveling inside .m4a or .mp4 files.
An .m4a file is an MPEG-4 container that holds only audio, most often AAC and occasionally Apple Lossless. Apple coined the .m4a extension so audio would not be confused with .mp4 video, and it remains the default for iTunes purchases, Apple Music downloads, and Voice Memos. For this route the practical draw is real tagging and artwork support, unlike bare .aac streams and gapless playback metadata for continuous albums — balanced against the extension hides whether the contents are lossy or lossless, muddying quality expectations, which is worth knowing before you commit a large batch.
Why convert AAC to M4A?
The practical trigger for this conversion is usually a mismatch: with .aac, raw ADTS files handle tags and cover art poorly. Switching to .m4a buys you real tagging and artwork support, unlike bare .aac streams, which is why it is the better fit for managing music inside iTunes and Apple Music libraries. Because the conversion runs locally, trying it costs nothing but a few seconds of compute on your own machine.
AAC vs M4A at a glance
| Aspect | AAC audio (.aac) | MPEG-4 audio (.m4a) |
|---|---|---|
| Format type | Lossy — discards detail it judges invisible to shrink files | Lossy — discards detail it judges invisible to shrink files |
| How it stores data | a pure MDCT transform codec, free of the hybrid filterbank compromise that limited MP3 | an ISO base media container restricted to audio tracks, structurally a sibling of MP4 |
| Strongest at | receiving the audio track copied out of MP4 video without re-encoding | managing music inside iTunes and Apple Music libraries |
| Weak spot | raw ADTS files handle tags and cover art poorly | the extension hides whether the contents are lossy or lossless, muddying quality expectations |
| Metadata | no standard tag container exists for raw ADTS streams; ID3 tags are sometimes prepended but poorly supported, so wrapping in .m4a is the reliable way to tag AAC | iTunes-style metadata atoms: title, album, artwork, composer, BPM, and the iTunSMPB gapless-playback data |
Pick M4A as the output
Select .m4a in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if M4A is selectable, the route is real and validated.
Convert on your device
Press Convert. The transcode runs on an FFmpeg engine compiled to WebAssembly, so the audio never leaves your device.
Verify and download
Each result is signature-checked before the download unlocks, so a failed encode can never masquerade as a valid M4A file. Outputs keep the original filename with the .m4a extension.
AAC to M4A questions, answered
Will converting AAC to M4A lose quality?
A second lossy step always costs a little, because aac is lossy-oriented and m4a is lossy-oriented and each encoder discards detail differently (generation loss). At the default quality the difference is rarely visible; avoid repeated round-trips between .aac and .m4a.
Is it private to convert AAC files here?
Yes — the .aac file is processed inside your browser tab and never uploaded. The transcode runs on an FFmpeg engine compiled to WebAssembly, so the audio never leaves your device. Close the tab and the file is gone from memory.
Where will the M4A file work?
Browsers, Windows, Android, and every Apple device play AAC-based .m4a files without extra software. The ALAC-filled variety is slightly narrower, since some inexpensive devices decode only the AAC form.
Will the M4A file be bigger or smaller than my AAC?
It depends on the content: an ISO base media container restricted to audio tracks, structurally a sibling of MP4. Convert one representative file first and compare before batch-processing a large set.
What happens to the metadata in my AAC file?
This converter strips container metadata deliberately (the FFmpeg command runs with metadata mapping disabled) so exported files do not leak recording details. In the source, no standard tag container exists for raw ADTS streams; ID3 tags are sometimes prepended but poorly supported, so wrapping in .m4a is the reliable way to tag AAC; none of it is transmitted anywhere because the file never leaves your browser.
Can I convert M4A back to AAC?
Yes — the reverse route exists as a separate tool. Bear in mind that round-tripping .aac → .m4a → .aac is not a perfect undo when any lossy step is involved; keep your original if fidelity matters.