AAC to MP3 Converter
Your AAC audio, playable everywhere. Drop AAC files, get MP3s back — 100% in your browser. No uploads, no accounts, no limits.
AAC sounds great and plays almost nowhere outside Apple and Android — phones, car stereos, email, and transcription tools all expect MP3. This converts raw .aac (ADTS) files and AAC in .m4a/.mp4 containers on your device, privately, including HE-AAC.
Honest limits: AAC is already compressed, so the MP3 is often about the same size — you convert for compatibility, not to save space; tags are not carried over; MP3 is lossy, so 320 kbps keeps the most.
Drop your AAC files (.aac / .m4a / .mp4) here
or — multiple recordings welcome, or paste a copied file
Up to 100 MB per file · up to 15 minutes per recording · up to 20 files per batch · nothing ever uploads
Privacy proof — verify it yourself
This page processes your recordings entirely on your device. All JavaScript and the engine are bundled locally. Your file data never leaves the device — the only third-party requests are the site’s own analytics (Google Analytics and a Cloudflare beacon), which load when the page opens and never see your files. Your recordings are personal; they never leave the machine you are sitting at.
Requests during processing: 0 to this site (the converter engine, fetched in two parts on first use) · 0 to anyone else (none — as it should be)
Converter engine: ffmpeg.wasm — loads on first convert
- Press F12 to open developer tools, then open the Network tab.
- Drop an AAC file above and let it convert.
- Watch the Network tab: no requests while it converts. The counter above shows the same split live. (The page’s own analytics load once when the page opens — before you start — and never touch your files.)
- Bonus: turn your internet off after the page loads and the engine has loaded once — conversion still works.
How to convert an AAC file to MP3 without uploading it
- Drop the .aac, .m4a or .mp4 files above — up to 20 at once. Each file’s codec (AAC-LC or HE-AAC), sample rate, channels, length and bitrate are shown straight away, with an estimated MP3 size at your chosen bitrate.
- Pick a bitrate — or a preset. Speech / voice memo (128 kbps) for spoken recordings, Music (192 kbps) for songs, Best quality (320 kbps) when you want to keep the most detail. Or drag the custom slider to any bitrate from 64 to 320 kbps — matching the AAC’s own bitrate is the smartest choice.
- Listen to each MP3 in the built-in preview, then download it — or grab everything as one ZIP. Your originals are untouched and nothing leaves your device.
Why convert an AAC at all?
AAC is the default audio codec of Apple and Android — iTunes, iPhone voice memos, YouTube audio, and most Android recordings are AAC. It sounds excellent for its size, but half the world cannot play it: Windows Media Player, older car stereos, email clients, and most transcription tools only accept MP3. Converting trades a little quality for a file that plays practically anywhere. Keep the AAC as your master copy and share the MP3.
Raw .aac files welcome here
A raw .aac file is an ADTS stream — AAC frames one after another with no container around them. Radio recordings, voice-recorder apps, and exports from audio tools often produce exactly this, and most converters refuse it because there is no container to read. This tool reads the ADTS frames directly (profile, sample rate, channels, frame count), so a raw .aac converts here — even one carrying an ID3 tag in front of the audio, which some encoders add. If your file is AAC inside an MP4 container instead, that converts here too.
What about .m4a files?
The M4A to MP3 Converter is tuned for iPhone voice memos (speech bitrates, long memos). This tool converts .m4a and .mp4 files as well — its distinct value is raw .aac ADTS files and AAC-in-MP4, plus per-file AAC info (profile, sample rate, channels) and HE-AAC handling. Use either one for an .m4a; use this one for a raw .aac.
HE-AAC: what the card shows
Low-bitrate AAC is often HE-AAC (also called AAC+ or aacPlus): the file stores a low-rate core — say 22.05 kHz mono — plus extra SBR data that rebuilds the full 44.1 kHz stereo sound when decoded. The card shows the core rate from the file header, because that is what the file actually declares; the MP3 still comes out at the full output rate. Measured in testing: a HE-AACv2 file whose header says 22.05 kHz mono decoded to a 44.1 kHz stereo MP3, and a Nero HE-AAC file in MP4 did the same. For raw .aac files the header cannot tell HE-AAC from plain LC at all, so the card shows the header values and the MP3 reveals the full rate once converted.
Honest limitations
- MP3 is lossy, always — there is no lossless MP3 mode. 320 kbps preserves the most; 128 kbps is fine for speech but audible on music.
- AAC is already compressed — the MP3 is often about the same size as the AAC, and can be a little bigger if you pick a higher bitrate than the AAC’s own. The page shows the before and after size on every file, so the result is never a surprise.
- Metadata is stripped — titles, artists and any iTunes tags in an M4A or ID3 tags on a raw .aac file are removed from the MP3 (verified in testing). Keep the original if you need the tags.
- 100 MB / 15-minute caps — in-browser encoding runs slower than real time for long files, so a longer recording would outlast a browser tab session. Split very long recordings first.
- First convert loads the engine — the converter (ffmpeg.wasm, ~31 MB) downloads once from this site on your first conversion. After that it is cached and works offline.
- Low sample-rate AACs cap the bitrate — an 8 kHz or 11,025 Hz recording encodes at most 64 kbps even if you pick 128, and a 22,050 Hz recording at most 160 kbps, because the encoder caps it (measured in testing). The card tells you when this happens.
- Renamed files are refused — an MP3, FLAC, WAV or Ogg file renamed to .aac is detected from its contents and refused with a clear message pointing at the right converter. A PNG image renamed to .aac is refused too.
- Protected files are refused — .m4p files from the old iTunes Music Store, and MP4 files with a protected (drms/enca) audio track, are encrypted with DRM and cannot be converted by any tool.
- Not all MP4 audio is AAC — an MP4 holding ALAC or MP3 audio is refused with a clear message, as is a video-only MP4 with no audio track. Only AAC audio in MP4/M4A containers is supported.
- HE-AAC shows its core rate — the card shows the core sample rate from the file header; the MP3 comes out at the full output rate (measured: a 22.05 kHz mono HE-AACv2 header decoded to 44.1 kHz stereo).
- MP3-only output — this tool makes MP3s. If you need FLAC or WAV, use a desktop converter.
Frequently asked questions
How do I convert an AAC file to MP3 without uploading it?
Use a tool that converts locally in your browser. This converter loads your AAC file into your device’s memory, decodes it with ffmpeg.wasm running on your machine, and encodes it as MP3 — all with JavaScript and WebAssembly running locally. Your file data never leaves the device — the only third-party requests are the site’s own analytics (Google Analytics and a Cloudflare beacon), which load when the page opens and never see your files. You can verify it by watching the Network tab in your browser’s developer tools while it converts — the live counter on this page shows no requests during processing.
What is an AAC file — raw .aac, .m4a and .mp4?
AAC is a codec, not a container: the same AAC audio can live as a raw ADTS stream in a .aac file (radio recordings, voice-recorder apps, exports from audio tools) or inside an MP4 container as .m4a (iTunes, iPhone) or .mp4. This converter handles both — it reads the file’s contents to tell a raw stream from a container, it does not trust the extension. Low-bitrate AAC is often HE-AAC, which stores a low-rate core plus extra data that rebuilds the full sound: the card shows the core rate from the file header (for example 22.05 kHz mono), and the MP3 comes out at the full output rate (44.1 kHz stereo in our tests). Protected .m4p files from the old iTunes Music Store are refused — their audio is encrypted and no tool can convert them.
Will converting AAC to MP3 lose quality?
Yes, a little: AAC is already lossy, so converting to MP3 is lossy-to-lossy and discards a little more detail — there is no lossless MP3 mode. In practice the difference is small when the bitrates match: at 192 kbps music still sounds very good, and at 320 kbps the difference from the AAC is inaudible for almost everyone. The mistake to avoid is re-encoding a low-bitrate AAC at a high MP3 bitrate — a 64 kbps voice recording re-encoded at 320 kbps just gets bigger, not better. Match the MP3 bitrate to the AAC’s own bitrate (shown on each file card) and keep the AAC as the master copy.
Why is my MP3 bigger than the AAC file?
Because AAC is already compressed — AAC is a newer, more efficient codec than MP3, so an AAC at a given bitrate is often smaller than an MP3 at the same bitrate. If your AAC was encoded at 64 kbps and you convert it at the default 192 kbps, the MP3 comes out roughly three times bigger while sounding no better, because the detail was already gone. That is expected, not a bug: pick a bitrate close to the AAC’s own bitrate (each card shows it) and the MP3 lands about the same size. You convert for compatibility — MP3 plays on phones, car stereos, email and transcription tools that never learned AAC — not to save space.
Do MP3s keep my AAC file’s tags and metadata?
No — tags and metadata are not carried over. The converter strips all metadata from the MP3 (titles, artists, and any iTunes tags in an M4A or ID3 tags on a raw .aac file), which was verified in testing: an M4A carrying a title tag produced an MP3 with no trace of that title. That is partly a privacy win, but if you need the tags, keep the original AAC alongside the MP3.
Can I convert a long AAC recording — how long and how big?
Up to 15 minutes and 100 MB per file, and up to 20 files per batch. Conversion runs in the browser via WebAssembly and scales roughly with length: in our test run a 3-second AAC file encoded in about 0.2 seconds once the engine had loaded, so a 9-minute recording takes on the order of half a minute on a typical laptop. Longer files take longer — split very long recordings first.
What bitrate should I choose — and what is the custom bitrate slider for?
Speech / voice memo (128 kbps) for spoken recordings, Music (192 kbps) for songs, Best quality (320 kbps) when you want to keep the most detail. The custom slider covers every valid MP3 bitrate from 64 to 320 kbps, so you can match the MP3 bitrate to the AAC’s own bitrate — a 96 kbps voice recording converts best at 96 kbps, not 320. One honest limit: low sample-rate sources cap the bitrate — an 8 kHz or 11,025 Hz recording encodes at most 64 kbps even if you pick 128, and a 22,050 Hz recording at most 160 kbps, because the encoder caps it (measured in testing). The card tells you when this happens.
How do I verify my files really never upload?
Open your browser’s developer tools (F12), go to the Network tab, then convert a file. You will see no requests during processing — the live counter on this page shows the same number. The only requests during processing are the converter engine itself (ffmpeg.wasm, about 31 MB), fetched in two parts from this same site on first use. All JavaScript and the WebAssembly engine are vendored locally. The only third-party requests are the site’s own analytics (Google Analytics and a Cloudflare beacon), which load when the page opens — they never see your files.