Audio tools that never upload your files.

Convert, trim, join, boost, slow down, compress, remove vocals, add reverb, read aloud and transcribe — right here in your browser. Free, with no account and no limits.

  • No uploads
  • No account
  • No usage limits
  • Open source, MIT
Drop an audio or video fileStart with an audio or video file
It's analyzed in this tab, and we suggest the right tool for it.

What should happen to your sound?

Each tool shows what it does to the waveform.

Convert Change the format of any recording. Audio or video to MP3, M4A, WAV, FLAC Trim Keep only the part you need. Visual waveform, exact timestamps Join Merge several files into one. Reorder, crossfade up to 3 s Boost volume Make quiet audio louder, or normalize it. Up to 500%, soft limiter Change speed Slow down or speed up, pitch stays put. 0.25× to 4× Compress Make the file smaller for email or chat. MP3 at 64–320 kbps Read aloud Turn written text into speech. 50+ languages, adjustable voice Transcribe Turn speech into text, privately with Whisper. Files, recordings or live dictation Remove vocals Split a song into the music and the voice. Karaoke track and acapella Slowed + reverb A slower, deeper version in a big room, or sped up. Hear it as you adjust

Where your file goes

Nowhere you can't see. Every step runs inside the browser tab you're reading this in.

Your file

On your computer or phone

This browser tab

Decodes, edits and encodes the audio with Web Audio and WebAssembly

Your downloads

The result, saved by your browser

A serverThere isn't one. AudioTools.dev is a set of static pages.

Check it yourself

Open your browser's developer tools, go to the Network tab and process a file. No request carries your audio.

Read every line

The code is open source under the MIT license. See it on GitHub or read how it works.

For your terminal, from the same author

AudioTools.dev — free browser-based audio processing

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.

How each tool works

Audio Converter

Convert audio (WAV, FLAC, OGG, AAC, M4A, WebM) or the soundtrack of a video (MP4, MOV, MKV) to MP3, M4A, WAV or FLAC. The audio converter reads the file in pieces with the browser's built-in codecs, then re-encodes it in the target format. WAV encoding is native and MP3 uses the LAME encoder (lamejs). File sizes up to several hundred MB are supported depending on your device's memory.

Voice to Text

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.

Text to Speech

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.

Audio Trimmer

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 MP3 or WAV. Uses OfflineAudioContext for precise sample-accurate trimming.

Audio Speed Changer

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.

Volume Booster

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.

Audio Joiner

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 MP3 or WAV.

Audio Compressor

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.

How browser audio processing works

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.

Privacy & security

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.

Also check out our developer tools at DevToolKit.site — 21 free browser-based tools for JSON formatting, JWT decoding, PostgreSQL config generation, and more.

Frequently asked questions

Are AudioTools really free?
Yes, all tools are completely free with no limits, no ads, and no sign-up. The entire project is open source under the MIT license.
Are my files uploaded to a server?
No. Every tool processes audio in your browser, so your files never leave your device. The one exception is live dictation in Voice to Text: it uses your browser's speech engine, which Chrome and Safari may run on Google's or Apple's servers. Private mode does not.
What audio formats are supported?
The tools read WAV, MP3, FLAC, OGG, AAC, M4A and WebM, or anything else your browser can decode; the converter also takes video (MP4, MOV, MKV). The converter saves MP3, M4A, WAV or FLAC, the other tools MP3 or WAV.
Does voice-to-text work offline?
Private mode does: Whisper runs in your browser, and after the model downloads once it works without a connection. Live dictation uses your browser's speech engine, which in Chrome and Safari may run on Google's or Apple's servers. Once a page has loaded, the other tools also work without a connection.
Can I use AudioTools on mobile?
Yes. All tools work on mobile browsers including Chrome on Android and Safari on iOS. The interface is fully responsive.
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