Convert, trim, transcribe, and synthesize audio — all in your browser. No uploads, no accounts, no usage limits — MIT-licensed, so you can check the code yourself.
Use the tools online, or download and run them locally. Contribute, fork, build upon — it's MIT licensed.
AudioTools.dev is a collection of free, open-source audio tools that run entirely in your browser. No files are uploaded to any server — all processing happens locally using modern Web APIs (Web Audio API, Web Speech API, MediaRecorder API). Every tool is free, with no limits, no ads, and no account required.
Convert between WAV, MP3, FLAC, OGG, AAC, M4A, and WebM formats. The audio converter decodes your audio file using the Web Audio API, then re-encodes it in the target format. WAV encoding is native, MP3 uses the LAME encoder compiled to WebAssembly, and FLAC uses a custom WASM encoder. File sizes up to several hundred MB are supported depending on your device's memory.
Real-time speech transcription using the Web Speech Recognition API. The voice-to-text tool supports 60+ languages including English, Spanish, French, German, Japanese, Chinese, Korean, Russian, Arabic, Hindi, and many more. Punctuation and formatting are automatic. Great for transcribing meetings, lectures, interviews, and voice notes. Private mode transcribes audio files and recordings with the Whisper speech model running entirely in your browser — the audio never leaves your device.
Convert written text to natural-sounding speech using the Web Speech Synthesis API. The text-to-speech tool offers 50+ voices across dozens of languages. Adjust speed (0.25x to 3x), pitch, and volume. Useful for proofreading, language learning, accessibility, and content creation.
Cut and trim audio files with a visual waveform editor. The audio trimmer shows your file as a waveform — drag the start and end handles to select the portion you want, preview the selection, and download the result as WAV. Uses OfflineAudioContext for precise sample-accurate trimming.
Slow down or speed up audio from 0.25x to 4x without changing pitch. The audio speed changer uses a WSOLA (Waveform Similarity Overlap-Add) time-stretching algorithm, so voices stay natural instead of sounding like chipmunks. Useful for language learning, transcription, and practising music.
Make quiet recordings louder — boost up to 500% or normalize to a consistent peak level. The volume booster applies a soft limiter when you push past the ceiling, so peaks are rounded off instead of crackling. Good for phone recordings, podcasts, and audiobook chapters.
Merge multiple audio files into one track. The audio joiner lets you reorder tracks by drag and drop, mix different formats, and add a crossfade between tracks for seamless transitions. The result is saved as WAV.
Reduce audio file size by re-encoding to MP3 at the bitrate and sample rate you choose. With the audio compressor, a 44 MB WAV can become about 4 MB at 128 kbps — handy for email attachments and messaging apps.
Modern browsers include powerful audio processing capabilities through the Web Audio API. When you load a file, the browser decodes it into raw PCM audio data (an AudioBuffer). This data can then be processed — trimmed, converted, analyzed, or played back — entirely in JavaScript. The result is encoded back into a file format and downloaded. No network requests are made during processing.
Your audio files never leave your device: there is no server-side processing and nothing is uploaded. The site uses Google Analytics for anonymous page-view statistics only — it never sees your audio or the files you process (see the privacy policy). The entire source code is available on GitHub under the MIT license for full transparency.
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