What is the AVR file format?
.avr files are associated with the Audio Visual Research software application. Files with the .avr extension store audio tracks in a binary container identified by the four-byte magic signature 2BIT at byte offset 0. A fixed 128-byte header precedes the raw audio samples, recording the channel count, bit depth, sample rate, loop points, and an optional 8-character name. All multi-byte header fields use big-endian byte order.
The format was popular among Atari ST users, for which platform the Audio Visual Research software was available, and also saw use on early Apple Macintosh systems. The AVR standard supports encoding audio data in stereo (two channels) or mono (single channel) using 8-bit or 16-bit sampling at any sample rate, stored as uncompressed PCM with no compression or encryption. Stereo data is stored as interleaved left/right samples immediately after the header.
.avr files are rarely seen anymore. They can be converted to more widely supported formats such as .WAV or .AIFF using tools such as Audacity or Awave Studio. In this way, users can still access old Atari ST-era audio tracks for archival or playback purposes.
Security & safety
RISK: LOWBinary PCM audio format; no executable code or scripting. Safe to open. Only risk is malformed files triggering bugs in legacy audio software.
Format details
in a nutshell- Atmel AVR Assembler Source - Some Atmel AVR microcontroller assembly source files use .avr extension; entirely unrelated to this audio format.
Programs that open AVR files
Windows3 apps
VLC media player
Open-source Drag the .avr file onto VLC; it will attempt to play raw PCM (may need codec hints). 
Audacity
Open-source File → Import → Raw Data - specify bit depth, channels, sample rate matching the header; no native .avr decoder. 
macOS2 apps
Linux1 app
Technical details
deep spec| Magic bytes | 32 42 49 54 ("2BIT") at offset 0 |
| Format type | Binary raw PCM audio with fixed 128-byte header |
| Encoding | Binary, big-endian (all multi-byte header fields) |
| Audio codec | Uncompressed PCM (no compression) |
| Channel support | Mono (single channel) or stereo (two-channel interleaved) |
| Bit depth | 8-bit (unsigned convention) or 16-bit (signed) |
| Sample rate | Any; stored as 32-bit value in header; typical range 8,000 - 44,100 Hz |
| Header size | Fixed 128 bytes, containing name (8 chars), channel flag, bit depth, loop points, MIDI note, sample rate |
| Platform | Atari ST, Classic Mac OS |
| Typical file size | 10 KB - 5 MB |
| Released | circa 1988-1990, Atari ST / early Mac era |
| Latest version | single revision; format unchanged since ~1990 |
| Specification | fileformats.archiveteam.org |
AVR conversions
Community Q&A
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