AAC to Text: What the Format Is and Every Way to Transcribe It

How do you convert AAC to text?

AAC to text takes one of two paths: upload the file directly to a tool that lists .aac among its accepted formats, or convert it to MP3 first and upload that, the same workflow covered in our broader guide to transcribing audio to text. Which path is faster depends on whether the tool you already use accepts AAC by name.

AAC (Advanced Audio Coding) is a lossy audio codec, not a whole file type on its own. Per Wikipedia, it was designed as the successor to MP3 and "generally achieves higher sound quality than MP3 at the same bit rate." The same codec reaches you two different ways: as a raw ".aac" file, or packaged inside an MP4 container using the ".m4a" extension, the more common form per Wikipedia. If your file ends in .m4a instead of .aac, more tools will take it directly (more on that below).

That container distinction is the single fact every ranking page for this keyword skips, and it is the reason two people searching "aac to text" can need two different answers. One genuinely holds a raw .aac file. The other is holding an .m4a file, sees "AAC" mentioned somewhere in its properties, and searches the wrong term.

AAC's spread explains why a raw .aac file lands on a device in the first place. Wikipedia lists it as Apple's iTunes Store default, YouTube's audio codec, and the format Android 2.3 and later decodes natively, adding that by 2017 AAC "had become a de facto industry standard for lossy audio." A file recorded on an Android voice recorder, or pulled out of a video with an audio-extraction tool, is a more likely source of a genuine raw .aac than an iPhone, since Apple's own recorder exports .m4a instead.

Which tools accept .aac files directly?

Three tools verified today list AAC by name and cost nothing to try. TurboScribe's accepted formats, per its own FAQ, are "MP3, M4A, MP4, MOV, AAC, WAV, OGG, OPUS, MPEG, WMA, WMV, AVI, FLAC, AIFF, ALAC, 3GP, MKV, WEBM, VOB, RMVB, MTS, TS, QuickTime, and DivX," with AAC included outright. Its free tier gives 3 transcripts a day, no card required. Its Unlimited plan costs $10 a month billed yearly ($120 a year) or $20 a month billed monthly, raising the cap to 10-hour files.

SpeakNotes' free transcription tools list MP3, WAV, M4A, AAC, OGG, and FLAC among the formats they accept, per its site, with files capped at 5MB, free processing capped at 5 minutes of content, and no signup required. Those caps fit a short memo without paying; a longer recording needs its Pro plan or one of the other tools here.

InstantOwl accepts .aac natively too. Per InstantOwl's own upload documentation, accepted formats include .mp3, .mp4, .m4a, .wav, .ogg, .webm, .mov, .aac, and .flac, at up to 150MB per file, with files over 24MB automatically split before transcription. Full disclosure, InstantOwl is our product; more on where it fits below. InstantOwl is currently free to use.

One tool people commonly reach for does not take AAC at all. Per Microsoft's Transcribe support page, "Transcribe currently supports .wav, .mp4, .m4a, .mp3 formats." AAC is not on that list. If Word's Transcribe is the free-because-you-already-pay-for-365 tool you were hoping to use, an .aac file needs a rename or a real conversion first, covered below.

Tool	Accepts .aac	Free limit
TurboScribe	Yes	3 files/day, no card required
SpeakNotes	Yes	5MB/file, 5 min free, no signup
InstantOwl	Yes	150MB/file, currently free to use
Microsoft Word Transcribe	No	Convert to .wav, .mp4, .m4a, or .mp3 first

Is your AAC file actually an M4A?

Check the file extension before doing anything else. Most audio described as "AAC" that reaches an iPhone or a messaging app is actually saved with the .m4a extension, not .aac, since .m4a is the more common container for the same codec, per Wikipedia. If your file ends in .m4a, more tools accept it outright, and our M4A to text guide covers the free on-device transcript newer iPhones already generate before you upload anything at all.

A genuine raw .aac file, one with no MP4 wrapper, is more likely to come from an Android recorder app or an audio-extraction tool than from an iPhone. Either way, the fix is the same: confirm the extension in your file manager first, since that two-letter difference determines which tools accept the file without an extra step.

How do you convert AAC to text with ffmpeg?

If your tool of choice does not list AAC, converting first is a one-line fix. Per ffmpeg's own documentation, the output format is "guessed from the file extension for output files," so the command needs no extra flags:

ffmpeg -i voice-note.aac voice-note.mp3

Run that from a terminal in the folder holding the file, then upload the resulting MP3 wherever MP3 to text tools, or Word's Transcribe, already accept it.

ffmpeg is not preinstalled on macOS or Windows, worth knowing before you try to run that command. Per ffmpeg's download page, the project "only provides source code," pointing Windows users to community builds from gyan.dev or BtbN, and Mac users to static builds. Homebrew packages the same tool behind one command, brew install ffmpeg, per the Homebrew formula page.

If installing anything sounds like too much, converter.app offers a free, browser-based AAC to MP3 converter with no install required. Either path, ffmpeg or a browser converter, gets you to an MP3 that every tool named above, and most others, will accept.

Where does InstantOwl fit?

Full disclosure: InstantOwl is our product, and this is our blog. Most people converting an AAC file are handling someone else's audio: a downloaded track, an extracted podcast clip, a colleague's recording. The tools above cover that job well.

The exception is the person whose .aac file is their own voice, recorded on an Android device or an app that saves raw AAC instead of the more common .m4a. For that file, InstantOwl accepts it directly with no rename or conversion step, and turns it into an organized note with tasks pulled out automatically instead of a transcript alone to sort through by hand. InstantOwl is currently free to use.

Related reading

• M4A to text: the far more common container for the same AAC audio, and the free on-device transcript newer iPhones already generate.
• MP3 to text: every free and paid path once an AAC file is converted to the most universally accepted format.
• Transcribe audio to text: the wider landscape of transcription tools and their free tiers.