Convert MP3 to AAC Online
Convert MP3 to AAC (Advanced Audio Coding). Free, in your browser, no file uploads.
.mp3 · up to 100 MB
What you can do
MP3 to AAC: better quality, smaller size
Apple ecosystem
AAC is the native format of iPhone, iPad, iTunes, and Apple Music. Perfect compatibility.
100% private
Conversion happens in your browser with FFmpeg WebAssembly. No servers.
Better quality at equal bitrate
AAC outperforms MP3 in ABX double-blind tests at 128 kbps and 192 kbps.
Instant
No queues, no waiting. Direct conversion on your device.
How it works
Three steps, no hassle
Upload your MP3 file
Drag or select your .mp3 file. Up to 200 MB, no registration or account required.
Conversion in your browser
FFmpeg WebAssembly re-encodes the MP3 to AAC-LC using libfdk_aac or FFmpeg's native encoder. The process happens entirely on your device.
Download the AAC
Get an .aac or .m4a file ready for use in Apple Music, iPhone, iPad, Apple TV, and any compatible device.
FAQ
Got questions?
Technically, yes: AAC (Advanced Audio Coding) was designed as MP3's successor and offers better quality at the same bitrate. In double-blind listening tests, AAC at 128 kbps sounds better than MP3 at 128 kbps. The reason lies in AAC's more sophisticated psychoacoustic model, which uses higher-resolution transform windows (2048-point MDCT vs MP3's 1152 samples), more efficient stereo channel prediction, and improved spectral quantization. The transparency threshold (the point where most listeners cannot distinguish the compressed version from the original) for AAC-LC is around 128–160 kbps, while for MP3 it is between 192–256 kbps.
Yes, there is additional degradation in lossy-to-lossy conversions. When converting MP3 to AAC, the process is: decode the MP3 (obtain PCM audio) and then re-encode it as AAC. Decoding the MP3 recovers the audio with MP3 compression artifacts (pre-echo, high-frequency distortion, quantization noise). Those artifacts are passed to the AAC encoder as if they were legitimate signal. The result is audio with accumulated artifacts from two encoding stages. For conversions where quality is critical, best practice is always to start from the original uncompressed file (WAV, FLAC, AIFF) and convert directly to AAC. If you only have the MP3, using an AAC bitrate equal to or higher than the original MP3's bitrate minimizes additional degradation.
AAC has universal support in the Apple ecosystem since iTunes 4.0 (2003): all iPhones, iPads, iPods, Apple TVs, AirPods, and HomePods support it natively. Android has supported AAC since version 1.5 (Cupcake, 2009). Windows natively supports AAC in Windows 10 and later through Media Foundation. AAC is the default audio codec in YouTube, Apple Music, iTunes, Spotify (for high-quality streams), WhatsApp, and FaceTime. DCI digital cinema systems also allow AAC. The only environments where AAC may present issues are very old embedded systems and some low-end hardware players from the 2000–2008 era.
Recommendations by use case: 64 kbps for voice and podcasts (high telephone quality, perfect for dialogue); 96 kbps for music under casual or mobile listening conditions; 128 kbps for good-quality music (Apple iTunes standard until 2009, when it increased to 256 kbps); 192 kbps for high subjective quality; 256 kbps for most listeners with high-fidelity equipment (the current Apple iTunes Plus standard, adopted in 2009); 320 kbps as the practical maximum (diminishing returns vs. 256 kbps in ABX tests). For conventional stereo content, 256 kbps AAC-LC is the sweet spot between quality and size.
The main AAC profiles are: AAC-LC (Low Complexity), the most compatible and general-purpose profile; HE-AAC (High Efficiency AAC, also called AAC+ or aacPlus v1), which adds SBR (Spectral Band Replication) to improve efficiency at low bitrates (32–96 kbps), ideal for radio streaming and podcasts; HE-AAC v2 (also called aacPlus v2 or eAAC+), which adds PS (Parametric Stereo) to HE-AAC for very low bitrates (16–48 kbps), widely used in DAB+ broadcasting. For general use with high-quality music, AAC-LC at 256 kbps is the right choice. HE-AAC makes sense at 64–96 kbps when bandwidth or storage are limited. AAC is standardized in ISO/IEC 13818-7 (MPEG-2 AAC, 1997) and ISO/IEC 14496-3 (MPEG-4 AAC, 1999).
Apple launched iTunes and the iPod in 2001 and chose AAC as its primary audio format for both technical and commercial reasons. Technically, AAC offered better quality than MP3 at the same bitrate, allowing music to be sold at 128 kbps with subjectively superior quality. Commercially, the AAC licensing agreement with Via Licensing (the patent pool including Dolby, Fraunhofer, AT&T, Sony, and Nokia — the original developers of the standard published in 1997) was more favorable than MP3's with Thomson Multimedia and Fraunhofer. The iTunes Music Store, launched in April 2003, sold its first 1 million songs in the first 6 days, all in AAC format at 128 kbps. In 2009, Apple migrated the store to iTunes Plus: AAC at 256 kbps without DRM. MP3 patents finally expired in April 2017.
Convert MP3 to AAC: history, quality, and when to do it
AAC (Advanced Audio Coding) is a lossy audio compression standard developed jointly by Dolby Laboratories, Fraunhofer IIS, AT&T Bell Labs, Sony Corporation, and Nokia. It was published in 1997 as part of the MPEG-2 standard (ISO/IEC 13818-7) and later expanded in the MPEG-4 Audio standard (ISO/IEC 14496-3) in 1999. The explicit goal of AAC's development was to create a successor to MP3 (MPEG-1 Audio Layer III, 1993) that overcame its technical limitations. MP3 was designed to work with sampling rates of 32, 44.1, and 48 kHz and uses a hybrid filter bank (polyphase + 576-point MDCT). AAC was designed from scratch to support up to 48 audio channels, sampling rates from 8 to 96 kHz, and uses only MDCT with 2048 or 256-point windows depending on content, providing superior adaptive time-frequency resolution. AAC's psychoacoustic model is significantly more sophisticated than MP3's. AAC implements Gain Control, Temporal Noise Shaping (TNS, for improving the encoding of tonal audio like voices), and more efficient stereo channel prediction through M/S stereo (Mid/Side) and intensity stereo. In perceptual quality benchmarks using MUSHRA (Multiple Stimuli with Hidden Reference and Anchor, the ITU-R subjective audio evaluation methodology), AAC-LC consistently outperforms MP3 at equal bitrates. The subjective transparency threshold for AAC-LC in double-blind tests is around 128 kbps for most listeners, compared to 192–256 kbps for MP3.
AAC's mass adoption came with Apple iTunes. When Apple launched the iTunes Music Store in April 2003, it chose AAC at 128 kbps as the distribution format. The decision was significant: in 2003, MP3 was the dominant format and most portable players (including early iPods) primarily supported MP3. But Apple included native AAC support in all iPods from the second generation (2002). In 2009, Apple migrated the entire iTunes Store to the iTunes Plus format: AAC at 256 kbps without DRM (Digital Rights Management). Apple's adoption of AAC had a cascade effect: all iOS devices (iPhone, iPad, iPod Touch), macOS, tvOS, and watchOS have dedicated hardware for AAC decoding. The iPhone 3G (2008) included the first chip with hardware HE-AAC decoding. The modern streaming ecosystem uses AAC extensively: Apple Music distributes at 256 kbps AAC-LC; YouTube uses AAC for audio in its MP4 videos (128 kbps streams for standard quality, 192 kbps for high quality); Spotify uses AAC at 128/192/256/320 kbps depending on subscription level on iOS; FaceTime and WhatsApp audio use AAC or Opus for voice and video calls.
When converting from MP3 to AAC, it is important to understand the implications of lossy-to-lossy conversion. Unlike converting from a lossless format (WAV or FLAC) to AAC, where you start from artifact-free original audio, converting MP3 to AAC involves decoding the MP3 (recovering PCM with MP3 compression artifacts) and then re-encoding it as AAC. Typical MP3 artifacts are: pre-echo on musical transients like drum attacks, aliasing in high frequencies from the polyphase filter bank, and quantization noise granularity. The AAC encoder will receive those anomalies as if they were legitimate signal and compress them again, adding its own quantization artifacts. The technical recommendation is clear: if you have the original uncompressed audio (WAV, FLAC, AIFF, Apple Lossless), always use it as the source for generating AAC. If you only have the MP3, tips for minimizing additional degradation are: (1) use an AAC bitrate equal to or higher than the original MP3's bitrate to avoid adding aggressive additional quantization; (2) choose AAC-LC (Low Complexity profile), which is the most compatible and introduces the fewest additional artifacts in conversions from already-compressed sources; (3) avoid HE-AAC for conversions from MP3, as SBR (Spectral Band Replication) can interact poorly with MP3's high-frequency artifacts. For personal collection files where only the MP3 exists, this tool enables conversion with optimal settings.