How to Convert AAC to GSM — Quick & Free
Fast, instant AAC to GSM conversion. No signup required. Just drop your .aac file and get .gsm in seconds.
Batch Settings
お気に入りのアニメのサウンドトラックや、大切なビジネス会議の録音。それらがAAC形式で手元にあるものの、特定の携帯電話網での利用や、古いシステムでの互換性を考えると、GSM形式への変換が必要となる場面は少なくありません。特に、音声ファイルのサイズを極力抑えたい場合や、通信帯域が限られる環境での利用を想定する際には、GSMの効率性は大きな利点となります。当社の変換ツールは、音質の劣化を最小限に抑えつつ、迅速かつ正確にAACファイルをGSM形式へと変換します。複雑な設定は一切不要。アップロードしてボタンを押すだけで、すぐに目的のファイルが手に入ります。大切な音源を、必要な場所で、最適な形で活用できるよう、私たちがサポートいたします。
- ガラケー向け着信音作成
- ビジネス会議録音のデータ軽量化
- 同人音声作品の配布用フォーマット調整
日本では、特に古い世代の携帯電話（フィーチャーフォン、通称ガラケー）での音声ファイル再生において、GSM形式が指定されるケースがまだ見られます。また、通信コストを抑えたい用途で、この軽量な形式が選ばれることがあります。
About AAC to GSM Conversion
Short answer: yes, you can convert AAC to GSM online for free, and quality is well preserved with the right settings. Just upload your .aac file to CocoConvert, pick GSM as the output, and click Convert. The whole process takes seconds.
Now for the details. AAC (Advanced Audio Coding) offers better quality than MP3 at the same bitrate — the default codec for Apple devices. GSM is a widely used file format. Converting between these two formats lets you convert between formats quickly.
Your AAC file is decoded and re-encoded as GSM. Converting AAC to GSM maintains high quality with CocoConvert's optimised encoder settings.
CocoConvert runs entirely online — no software to install, no account to create. Your files are encrypted during upload (TLS), processed on isolated servers in Germany, and permanently deleted after 24 hours. It works in Chrome, Safari, Firefox, Edge, and all mobile browsers.
Need to convert more than one file? Free users can do 5 per hour. Pro gets 100 per hour with files up to 5 GB each.
How to Convert AAC to GSM
- 1
1. Upload AAC
Drop your .aac file onto the page (or tap "Browse" on mobile). Add multiple files for batch conversion.
- 2
2. Select GSM
Choose .gsm from the output dropdown. Settings are pre-configured for best results.
- 3
3. Convert
One click. The server handles all the heavy lifting using FFmpeg and Sharp.
- 4
4. Download
Your .gsm file is ready. Download it directly or get all files as a zip archive.
What Happens When You Convert AAC to GSM
Your AAC file is decoded and re-encoded as GSM.
Your AAC file is uploaded and validated
The file is decoded (parsed into its raw data)
The data is re-encoded in GSM format
The converted file is ready for download
Format Comparison
AAC
.aac file
| Extension | .aac |
| MIME Type | audio/aac |
| Category | Audio |
GSM
.gsm file
| Extension | .gsm |
| MIME Type | audio/gsm |
| Category | Audio |
Should You Convert AAC to GSM?
When to Convert
- ✓When you need a GSM file
Frequently Asked Questions
Is AAC to GSM conversion free?
Yes. CocoConvert offers free AAC to GSM conversion with generous daily limits — 25 minutes of processing time and up to 5 files per hour (250 MB each). Pro plans remove these limits.
How fast is AAC to GSM conversion?
Most files convert in 2–10 seconds depending on size. Large audio files may take 30 seconds. Batch jobs process in parallel for maximum speed.
What happens to my files after conversion?
Your uploaded AAC file and the converted GSM file are both automatically deleted from our servers within 24 hours. They are never shared, sold, or analysed.
Does converting AAC to GSM lose quality?
Converting AAC to GSM maintains high quality with CocoConvert's optimised encoder settings.
Can I convert GSM back to AAC?
Yes, CocoConvert supports GSM to AAC conversion as well. However, if the original conversion involved lossy compression, converting back won't recover the lost data.
Versions are pinned in our worker Dockerfile and re-built via CI on every change.