AMR
A speech-oriented audio format standardized for mobile communications, especially narrowband voice coding in cellular networks and voice recordings.
General information
- Format name
- Adaptive Multi-Rate Audio
- Extension
.amr- MIME type
audio/AMR- Category
- audio
- Data type
- Binary
- Developer
- 3GPP
Media properties
- Compression
- Lossy
- Codec
- AMR-NB
File signatures
| Offset | Hexadecimal | ASCII | Description |
|---|---|---|---|
| 0 | 23 21 41 4D 52 0A | #!AMR | Common magic string for AMR narrowband files stored in the single-channel file format. |
Common uses
Mobile voice recordings
Cellular speech
Voicemail
Telephony audio
Low-bitrate speech storage
Related formats
Technical resources
| Resource | Publisher | Link |
|---|---|---|
| RFC 4867 — RTP Payload Format and File Storage Format for AMR and AMR-WB Audio | RFC Editor | Open resource ↗ |
| Media Types Registry | IANA | Open resource ↗ |
Record information
- Verified
- October 4, 2026
- Last updated
- October 4, 2026