About GSM Files
GSM Audio
GSM 06.10 is a speech compression standard designed for the Global System for Mobile Communications. It encodes speech at 13 kbps using Regular Pulse Excitation with Long Term Prediction, optimized for voice intelligibility over cellular networks.
Family
Audio Files
Extension
.gsm
MIME Type
audio/gsm
Can Use As
47 53 4D 46 00 01 00 00 4B 41 49 4A
ASCII: GSMF....KAIJ
📈 Target Minimum File Size (Guaranteed ≥ KB)
Lossless JPEG Q100 + standard COM segment padding for government & exam portals
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HOW GSM CAME TO BE.
GSM — Global System for Mobile communications — standardized voice over digital cellular networks in 1987 in Europe. The codec specified for GSM calls compressed 8 kHz PCM speech into 13 kbps bitstream using Regular Pulse Excitation Long-Term Prediction (RPE-LTP). That was 6 kbps less than a typical landline call and shockingly better-sounding than anyone expected for the time. Every GSM phone on Earth — the 2G networks that spread from Europe to global coverage between 1991 and 2010 — decoded this codec continuously.
Standalone .gsm files preserve recorded calls in that same 13 kbps format. A minute of voice is about 100 KB. The extension appears mostly in corporate voicemail exports, old call-center archives, and some PBX recording systems. Newer LTE and VoLTE networks use Opus or EVS, but GSM’s codec survives in billions of 2G recordings and in the lo-fi-voice aesthetic of early-2000s phone memos.
Technical Specifications
- MIME type
- audio/gsm
- Extension
- .gsm
- Codec
- GSM 06.10 (RPE-LTP)
- Sample rate
- 8 kHz
- Bitrate
- 13 kbps
Typical Sizes & Weights
1 min of voice
~100 KB
1 hour voicemail archive
~6 MB
STRENGTHS & LIMITATIONS.
Strengths
- Tiny bitrate (13 kbps) — hours of speech in a few MB.
- Speech-optimized — clear voice reproduction.
- Universal cellphone decoder adoption 1991-2015.
- Stable since 1987.
Limitations
- Speech-only — music sounds distorted.
- 8 kHz sampling — narrowband, muffled by modern standards.
- Legacy — LTE VoLTE moved to AMR-WB, Opus, or EVS.
- Tooling outside telecom is sparse.
CURIOSITIES & TRIVIA.
The GSM codec compressed voice at 13 kbps — good enough for 4 billion subscribers by the time 2G peaked around 2010.
Finland's Nokia and Sweden's Ericsson built most of the first-generation GSM infrastructure — Europe's telecom standard went worldwide.
GSM audio at 8 kHz is deliberately mono and speech-only — trying to play music through GSM sounds notoriously awful.
Call-center PBXes often saved customer call recordings as .gsm for decades because the bitrate was so small.
Every iPhone can still encode audio as GSM 6.10 — a vestige of the codec's universal embedded-device presence.
Specialized Utilities for .GSM Files
MP3 Audio Compressor — Reduce MP3 File Size
Compress MP3, WAV, M4A, and FLAC audio files by adjusting bitrate (64k, 96k, 128k, 192k), sample rate, and mono/stereo channels.
Online Audio Cutter & Trimmer
Trim MP3, WAV, FLAC, M4A, and OGG audio tracks to exact start and end timestamps with built-in browser playback and custom bitrate.
Extract Audio from Video
Extract the audio track from any video file and save it as MP3, WAV, or other audio formats. Perfect for creating podcasts, music rips, or voice-only recordings.
Video to MP3 Audio Extractor
Extract high-bitrate MP3 audio tracks from MP4, MOV, MKV, AVI, and WebM video recordings in seconds—ideal for podcasts, lectures, and interviews.
CONVERT FROM GSM
Common Use Cases
Voice over cellular, telephony systems, low-bandwidth speech encoding
Related Formats
Popular comparisons
GSM vs MP3
Differences, file size, and when to choose each format.
GSM vs WAV
Differences, file size, and when to choose each format.
GSM vs FLAC
Differences, file size, and when to choose each format.
GSM vs AAC
Differences, file size, and when to choose each format.
GSM vs M4A
Differences, file size, and when to choose each format.
GSM vs OGG
Differences, file size, and when to choose each format.
Popular GSM conversions
The most-requested destinations when starting from GSM.
Frequently Asked Questions
GSM (GSM Audio) is an audio file format used to store sound recordings — music, voice, podcasts, sound effects. The format defines how the audio samples are compressed (or stored raw), what bitrates are supported, and how metadata such as title, artist, album, and cover art is embedded. It is part of the audio files family.
VLC, foobar2000, and the default media players on Windows and macOS handle GSM natively. On mobile, iOS Music and Android media apps vary in their support — popular formats work everywhere; niche ones may need a dedicated app. If playback fails on a device, converting to MP3 or AAC usually solves it.
Upload the GSM to KaijuConverter and pick MP3, WAV, FLAC, AAC, OGG, or any other target. Our FFmpeg pipeline decodes the audio and re-encodes to the target format at sensible default bitrates (VBR ~190 kbps for music, 96 kbps for speech). Metadata and cover art travel with the audio where both formats support them.
GSM can be lossy or lossless depending on the specific variant. Lossy variants (smaller files) discard some audio detail during compression in ways tuned to be inaudible; lossless variants preserve every sample exactly but produce larger files. For distribution, lossy at high bitrate is standard; for archival, lossless wins.
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