AAC Converter Free & Private
The modern successor to MP3. Convert AAC Audio files entirely in your browser — no upload, no account.
About AAC Audio
AAC (Advanced Audio Coding) is the default audio codec for Apple devices, YouTube, and most streaming services. Standardised as part of MPEG-2 and MPEG-4, it delivers better sound quality than MP3 at equivalent bitrates — particularly noticeable at lower bitrates where MP3 introduces audible artefacts. Every iPhone, iPad, and Mac records audio in AAC by default.
Technical details
| Container | ADTS (.aac) or MP4 container (.m4a) |
| Video codecs | N/A (audio only) |
| Audio codecs | AAC-LC, HE-AAC v1 (SBR), HE-AAC v2 (SBR+PS) |
| Max resolution | N/A |
| Streaming | HLS, DASH, HTTP streaming |
| Metadata | Limited in ADTS; full metadata in .m4a container |
Best for
Apple devices, streaming audio, podcasts on Apple Podcasts, YouTube uploads
Advantages
- Better quality than MP3 at the same bitrate
- Native codec for Apple ecosystem and YouTube
- Supports multichannel audio (5.1, 7.1)
- HE-AAC is excellent for very low bitrates (voice, streaming)
Limitations
- Raw .aac files (ADTS) have limited metadata support
- Some older devices prefer MP3
- Encoding quality varies significantly between implementations
Convert AAC to other formats
Convert other formats to AAC
AAC compatibility
All Apple devices, Android, most browsers, YouTube, Spotify, most streaming services
Why privacy matters for file conversion
Most online converters upload your files to remote servers where they may be scanned, stored, or shared. This tool is different — the conversion runs in your browser via WebAssembly or the WebCodecs API. Your files stay on your device. Always.
Brought to you by
Love keeping your files private? Utterly brings the same philosophy to audio. Transcribe meetings, lectures, and voice memos — entirely on your iPhone, iPad, or Mac.
Frequently asked questions
AAC is the codec (compression algorithm). M4A is AAC audio wrapped in an MP4 container, which adds metadata support (title, artist, cover art). For music files, M4A is preferred; raw .aac is used in streaming.
Yes, completely free with no file limits. The conversion engine runs directly in your browser — we have zero server costs for processing, so we can offer it at no charge.
Your file never leaves your device. The conversion engine runs 100% in your browser using WebAssembly or the WebCodecs API. We have no access to your files — no uploads, no logs, no data collection whatsoever.
On desktop browsers (Chrome, Firefox, Edge) files up to 500 MB convert reliably. On Safari (macOS) the practical limit is around 200 MB. On iPhone and iPad, keep files under 50 MB — iOS enforces tight memory limits for browser-based processing.
On your first visit, the browser downloads the conversion engine (24–50 MB depending on which backend is used). This is cached locally, so subsequent conversions load much faster.
Chrome, Edge, and Brave use hardware-accelerated WebCodecs when the format is supported — this is 5–10× faster than software encoding. For unsupported formats the tool falls back to ffmpeg.wasm, where Firefox typically performs best.
Utterly is a privacy-first transcription app for Apple devices. It uses on-device AI to transcribe and translate audio — no cloud, no subscription required to start. This free converter is brought to you by the Utterly team.