Convert Matroska Video (.mkv) to Advanced Audio Coding (.aac) online for free. Fast, secure video conversion with no watermarks or registration.
Conversion settings — add a file to adjust
Upload your .mkv file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .aac file when it's ready.
Extracting audio from an MKV file as AAC gives you a widely compatible audio stream that works on every Apple device, most Android phones, and all modern web browsers. Since many MKV files already contain AAC audio tracks, this conversion can often be a lossless remux rather than a transcode, preserving the original audio quality bit-for-bit.
MKV is a video container, and when all you need is the soundtrack, podcast audio, or dialogue from a recording, keeping the video data is wasteful. AAC extraction produces a compact audio file that plays natively on iOS, macOS, Windows, Android, and can be embedded in HTML5 audio elements without requiring any plugins or third-party apps.
AAC also serves as the standard audio format for iTunes, Apple Music uploads, and many podcast hosting platforms. If you are extracting interview audio, music performances, or lecture recordings from MKV screen captures, AAC at 128-256 kbps delivers transparent quality at roughly half the bitrate MP3 would need for equivalent fidelity thanks to its more efficient psychoacoustic model.
FFmpeg inspects the MKV container for existing AAC audio streams. If one is found, it performs a stream copy (-c:a copy) that extracts the AAC data without decoding or re-encoding, preserving perfect quality and completing in seconds. If the audio is in a different codec (Opus, FLAC, DTS, etc.), FFmpeg decodes it and re-encodes to AAC using the libfdk_aac or native AAC encoder at the specified bitrate. The output is wrapped in an ADTS or M4A container depending on the target extension.
When remuxing an existing AAC stream, quality is identical to the source since no transcoding occurs. When transcoding from lossless codecs like FLAC or PCM, AAC at 256 kbps is considered transparent (indistinguishable from the original in controlled listening tests). Transcoding from other lossy codecs like Vorbis or MP3 to AAC will introduce a small amount of generational loss, though at 192 kbps or above this is typically imperceptible.
| Device | MKV | AAC |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Native |
| iPhone/iPad | Partial | Native |
| Android | Partial | Partial |
| Linux | Partial | Partial |
| Web Browser | No |
Resolution: 1920x1080
Bitrate: 8-12 Mbps
H.264 recommended for fast processing
Resolution: 1080x1080
Bitrate: 3.5 Mbps
Square or 9:16 for Reels
Resolution: 1080x1920
Bitrate: 4 Mbps
9:16 vertical, under 60s ideal
Resolution: 1280x720
Bitrate: 5 Mbps
Under 140s, 512MB max
Resolution: 960x540
Bitrate: 2 Mbps
16MB limit for standard, 64MB for document
Resolution: 1280x720
Bitrate: 4 Mbps
MKV to AAC is one of the most efficient audio extractions you can perform, often completing without any quality loss when the source already contains an AAC track.
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| No |
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| Ominaisuus | MKV | AAC |
|---|---|---|
| Koko nimi | Matroska Video | Advanced Audio Coding |
| Tiedostopääte | .mkv | .aac |
| Paras käyttökohde | Multiple audio tracks | Superior to MP3 |