Convert M4A to AAC Online
Extract raw AAC from the M4A container. Free, in your browser, no file uploads.
.m4a · up to 100 MB
What you can do
Extract the pure AAC stream from the M4A container
No re-encoding
AAC is extracted from the M4A container without modifying a single audio bit. Zero quality loss.
100% private
Your M4A files never leave your device. Extraction happens in your browser.
ADTS for streaming
AAC is delivered in ADTS format, compatible with HLS, embedded systems, and hardware decoders.
Container vs. codec
M4A is the MP4 wrapper; AAC is the actual audio. This tool separates one from the other.
How it works
Three steps, no hassle
Upload your M4A file
Drag or select the .m4a from iTunes, Apple Music, or any audio recorder. No signup, no installs.
AAC extraction in the browser
The AAC audio stream is extracted from the MPEG-4 container and wrapped in ADTS format directly on your device.
Download your AAC
Raw AAC ready for streaming, embedded systems, players that don't accept the M4A container, or technical inspection.
FAQ
Got questions?
The confusion is completely understandable and very common. M4A and AAC refer to the same audio data in terms of quality, but are conceptually distinct: AAC (Advanced Audio Coding, ISO/IEC 14496-3) is the audio codec — the compression algorithm that encodes audio samples. M4A is simply a file extension indicating that an MPEG-4 Part 14 (MP4) file contains exclusively audio. Technically, a .m4a file is an MP4 container (.mp4) holding an AAC audio stream. The container vs. codec distinction is fundamental: the container (M4A/MP4) provides metadata, timestamps, index structure — what the OS sees as 'file type'; the codec (AAC) is the actual audio data. It is exactly the same relationship as MKV (container) and H.264 (video codec), or MP4 (container) and HEVC (codec).
Cases where raw AAC (in ADTS, Audio Data Transport Stream format) is needed instead of M4A include: (1) audio streaming on media servers using the HLS (HTTP Live Streaming) protocol — HLS .ts segments with AAC audio use ADTS; (2) embedded systems with hardware AAC decoders that don't include an MP4 container parser (DSP processors in IP cameras, security recorders, IoT devices); (3) audio analysis tools that directly inspect the AAC bitstream (for example, to verify AAC frame parameters: sample rate, channel configuration, AAC-LC vs HE-AAC profile); (4) audio processing pipelines that chain tools working with raw audio streams without a container.
ADTS (Audio Data Transport Stream) is the simplest encapsulation form for the AAC bitstream: each AAC frame is preceded by a 7 or 9-byte header (depending on whether CRC is included) that specifies the AAC profile version (AAC-LC, HE-AAC), sample rate, and channel configuration. ADTS allows decoding from any point in the stream without needing to parse a full container, making it ideal for streaming and resource-limited devices. The alternative format is LATM/LOAS (Low-overhead Audio Transport Multiplex), used primarily in DVB and some IPTV contexts.
No. M4A files purchased from the iTunes Music Store before 2009 and some Apple Music files with FairPlay DRM (Apple's Digital Rights Management) have encrypted audio. Only DRM-free M4A files are convertible: this includes iTunes Plus files (DRM-free, sold on iTunes since 2007), self-recorded M4A files, and any M4A downloaded from DRM-free sources. Apple Music streaming content does not generate a downloadable DRM-free .m4a.
There is no audio quality loss if conversion is a demultiplex without re-encoding — which is exactly what this converter does. The process extracts the AAC stream from the MP4 container and encapsulates it in ADTS without modifying a single bit of audio. It is equivalent to extracting a file from a ZIP archive: the content doesn't change, only the wrapper. This is called 'remux' or 'stream copy' in media processing terminology.
ADTS .aac files are widely compatible: VLC, iTunes/Music, Windows Media Player (with codecs installed), QuickTime, foobar2000, and most Android and iOS players open them without issues. Some older hardware players or those with stricter AAC implementations may prefer AAC in an M4A container. For maximum compatibility in home and car players, the original M4A is generally more universally accepted than raw AAC.
Convert M4A to AAC: extract the pure audio stream from the MPEG-4 container
The distinction between M4A and AAC is one of the most frequent misunderstandings in digital audio processing, and understanding it requires grasping the difference between codec and container. AAC (Advanced Audio Coding) is an audio codec jointly developed by Bell Labs, Dolby Laboratories, Fraunhofer IIS, Sony Corporation, and Nokia, standardized as ISO/IEC 13818-7 (MPEG-2 AAC) in 1997 and subsequently as ISO/IEC 14496-3 (MPEG-4 AAC) in 1999. AAC was designed as the successor to MP3 (MPEG-1 Audio Layer III), offering better quality at the same bit rate — specifically, AAC-LC at 128 kbps delivers subjectively equivalent quality to MP3 at 192 kbps according to blind listening tests conducted by Fraunhofer in 1998. M4A, on the other hand, is simply a file naming convention: a .m4a file is an MPEG-4 Part 14 file (the ISO/IEC 14496-14 container specification, an extension of the QuickTime .mov container) containing exclusively audio. Apple introduced the .m4a extension in iTunes to distinguish MPEG-4 audio files from MPEG-4 video files (.mp4, .m4v). The relationship is analogous to how a letter envelope is the container and the letter is the content: M4A is the envelope, AAC is the letter.
The need to extract raw AAC from the M4A container arises in specific technical contexts where the MP4 container parser introduces overhead or incompatibility. The most important case in 2025 is audio streaming via HLS (HTTP Live Streaming, a protocol developed by Apple in 2009 and standardized by IETF as RFC 8216 in 2017). Audio segments in HLS playlists use AAC audio in ADTS (Audio Data Transport Stream) format inside MPEG-TS containers (.ts), not in M4A. When an audio publishing pipeline needs to prepare M4A content for HLS distribution, the first step is extracting the AAC stream from the M4A container and segmenting it into ADTS for the MPEG-TS chunks of the HLS stream. The second relevant technical context is embedded systems processing: hardware AAC decoders present in DSP processors of IP cameras (Hikvision, Dahua), NVR security recorders, and IoT audio devices frequently implement only the ADTS decoder without an MP4 container parser, because adding the MP4 parser in firmware with limited ROM adds unnecessary complexity when only continuous streaming audio is needed.
The technical process of extracting AAC from M4A is conceptually a remux or stream copy: rather than decoding the audio to PCM and re-encoding it to AAC (which would introduce additional quality loss), the AAC bitstream is read directly from inside the MP4 container and encapsulated in ADTS without modification. The internal structure of an M4A file follows the box (atom) specification of the MPEG-4 container: an 'ftyp' box identifying the file type, a 'moov' box containing all track metadata (duration, sample rate, channel configuration, timestamps for each audio frame in the 'stts' box), and an 'mdat' box containing the compressed audio data. To extract the AAC, it is necessary to read the 'mdat' box and reconstitute the ADTS stream by prepending standard 7-byte ADTS headers in front of each AAC frame, using the configuration parameters (AudioSpecificConfig) read from the 'esds' box of the MP4 container. Convertir.ai performs this process entirely in WebAssembly inside the browser, without transmitting the file data to any external server. The result is bit-identical to the original AAC stream: every AAC frame has exactly the same bytes as in the source M4A, with the only difference being that they are now encapsulated in ADTS instead of in an MP4 container.