These are the open-source software and AI models FreeSoundTools uses. The full license texts are in the files linked below. Checked: October 3, 2026.
| Name (version) | Used for | License | Copyright notice and full text |
|---|---|---|---|
| OpenAI Whisper | Speech recognition model | MIT | Copyright (c) 2022 OpenAI · Full text · https://github.com/openai/whisper |
| Xenova/whisper-tiny·base·small (ONNX conversions) | Speech recognition model files | Apache-2.0 (as stated on the model card) | https://huggingface.co/Xenova/whisper-small (downloaded from Hugging Face) |
| Transformers.js 4.3.0 | Running models | Apache-2.0 | Full text · https://github.com/huggingface/transformers.js |
| ONNX Runtime Web | Model runtime engine (included with Transformers.js; runtime files are downloaded from jsDelivr) | MIT | Copyright (c) Microsoft Corporation · Full text |
| RNNoise (@shiguredo/rnnoise-wasm 2025.1.5) | Voice noise reduction | Apache-2.0 (wrapper), RNNoise is BSD-style | Copyright 2021-2025 Takeru Ohta, Shiguredo Inc. / RNNoise: Copyright (c) 2007-2017, 2024 Jean-Marc Valin, (c) 2023 Amazon, (c) 2017 Mozilla, (c) 2005-2017 Xiph.Org Foundation, (c) 2003-2004 Mark Borgerding · Full text |
| FreeSoundTools MP3 encoder (our own, 1.0.0) | Saving MP3 files | MIT | Source · Huffman table data from go-mp3 (Apache-2.0, https://github.com/hajimehoshi/go-mp3) |
The speech recognition models (Whisper) are used by the speech-to-text and subtitle tools, which are currently on our Korean site. The English tools use RNNoise (Voice Noise Remover) and our own MP3 encoder (MP3 saving).
MP3 saving (our own encoder)
This site saves MP3 files with an encoder we wrote from the public MPEG audio specification (ISO/IEC 11172-3 and 13818-3, Layer III), assets/dago-mp3.js, under the MIT license. No GPL/LGPL code such as LAME or lamejs is used, and the MP3 patents expired in 2017. The Huffman code values defined by the standard were taken from the table data published by go-mp3 (Apache-2.0). Short blocks are not used yet, so very sharp attacks (e.g. percussion) can show slight pre-echo.
Fonts
We don't download external web fonts; the site uses fonts installed on your device.
Trademarks and affiliation
OpenAI, Whisper, Microsoft, Hugging Face, Google, Cloudflare, Xiph.Org and other names are trademarks or names of their respective owners and are used only to identify the source. FreeSoundTools is not affiliated with or endorsed by them.