The codec inside almost every modern Apple audio file — M4A's engine, not a separate format of its own.
AAC (Advanced Audio Coding) is a compressed audio codec, not really a file format in its own right the way MP3 or WAV are — it describes how the audio data is encoded, while the .m4a extension is the container that actually holds it on Apple devices. AAC was designed as MP3's successor, delivering noticeably better sound quality at the same bitrate or the same quality at a smaller file size, and it became Apple's standard for Apple Music, iTunes purchases, Voice Memos, and podcasts as a result. A file that arrives with a literal .aac extension is typically a raw AAC audio stream without the M4A container wrapped around it — less common than M4A itself, but still something Bluetooth accessories, some Android apps, and certain streaming and broadcast tools produce directly. Practically, treating a .aac file is the same job as treating an M4A file, since the underlying audio format is identical; only the container differs.
iPhone, iPad, and Mac play AAC natively, whether it arrives as a raw .aac file or wrapped in the far more common .m4a container. Most Android phones, modern car stereos, and Bluetooth speakers decode AAC as well, since it's the standard codec behind Bluetooth's higher-quality audio profile.
A raw .aac file behaves like any compressed audio track — worth editing, trimming, or wrapping into a more universally recognized container. Filemorph edits and converts AAC audio the same way it handles M4A, entirely on-device.
Filemorph can convert AAC to M4A on-device — the standard container for the same AAC audio, recognized more consistently across apps than a raw .aac file.
Filemorph converts .aac files entirely on-device on iPhone, iPad and Mac — no upload, no account, and it works in Airplane Mode.
Relevant operations in Filemorph:
The audio codec is the same — AAC — in both cases. M4A is simply the standard container Apple uses to hold AAC audio, while a raw .aac file is the same encoded audio without that container wrapped around it.
AAC was designed as MP3's technical successor and delivers better sound quality at an equivalent bitrate, or the same quality at a smaller file size. Apple adopted it for Apple Music, iTunes purchases, and Voice Memos for that reason.
No. Filemorph trims, merges, and converts AAC audio entirely on-device, so a voice recording or downloaded track never leaves the iPhone or iPad, and the process works with no internet connection.