What is the ADTS file format?
An .adts file contains AAC (Advanced Audio Coding) audio packaged in the ADTS (Audio Data Transport Stream) framing format, standardised in MPEG-2 Part 7 (ISO/IEC 13818-7, 1997) and carried forward into MPEG-4 Part 3 (ISO/IEC 14496-3). Unlike container formats such as .mp4, ADTS has no global file header - every frame begins with a 12-bit sync word (0xFFF), making the stream self-synchronising so a decoder can lock onto any frame boundary without reading from the start of the file.
Each ADTS frame carries a 7-byte header (9 bytes when CRC protection is enabled) that encodes the AAC profile, sampling frequency index, channel configuration, and frame length, followed by the raw AAC audio data. Supported sample rates range from 8 kHz to 96 kHz; bitrates typically fall between 64 kbps and 320 kbps.
MPEG-4 AAC frames use the sync pattern 0xFFF1; the MPEG-2 AAC variant uses 0xFFF9. Most modern decoders handle both transparently.
ADTS is functionally equivalent to files using the .aac extension - IANA and most media players now prefer .aac for raw AAC streams, so .adts is encountered mainly in broadcast workflows and HTTP Live Streaming (HLS) transport segments. FFmpeg, VLC, and the majority of hardware media players decode .adts files natively.
Security & safety
RISK: LOWADTS/AAC files are audio data only. No macro or scripting capability. Negligible exploit surface in well-maintained players.
Format details
in a nutshellPrograms that open ADTS files
Windows4 apps
Windows Media Player
Built-in Double-click the .adts file; WMP handles AAC audio natively on Windows 10/11. 
macOS3 apps
Linux2 apps
Android1 app
Technical details
deep spec| Audio codec | AAC (Advanced Audio Coding) - lossy perceptual audio codec |
| Framing | ADTS (Audio Data Transport Stream) - self-synchronizing per-frame headers; no global file header |
| Sync word | 0xFFF1 (MPEG-4 AAC) or 0xFFF9 (MPEG-2 AAC) at every frame boundary |
| Frame header size | 7 bytes (no CRC; protection_absent=1) or 9 bytes (with 16-bit CRC per frame; protection_absent=0) |
| Byte order | Big-endian |
| Supported sample rates | 8 kHz - 96 kHz (12 discrete rates encoded via 4-bit sampling_frequency_index in ADTS header) |
| Channel support | Up to 48 channels (MPEG-4 AAC); typical files use 1 (mono) or 2 (stereo) channels |
| Typical bitrate | 64 - 320 kbps |
| Standards | MPEG-2 Part 7 (ISO/IEC 13818-7, 1997) and MPEG-4 Part 3 (ISO/IEC 14496-3) |
| MIME type | audio/aac (primary); audio/vnd.dlna.adts (DLNA); audio/aacp (HE-AAC) |
| CRC integrity | Optional 16-bit CRC per frame; enabled or disabled per-frame via the protection_absent bit in the ADTS header |
| Preferred alternative extension | .aac - IANA-recommended extension for raw AAC/ADTS streams; .adts deprecated in favour of .aac |
| Typical use case | HTTP Live Streaming (HLS) transport segments; broadcast audio distribution; raw AAC output from hardware encoders |
| Released | 1997 (MPEG-2 Part 7, ISO/IEC 13818-7) |
| Latest version | ISO/IEC 14496-3:2019 (MPEG-4 Part 3) |
| Open standard | Yes · royalty-free |
| Specification | www.iso.org |
ADTS conversions
Community Q&A
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