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Audio Speed Changer

Speed up or slow down browser-decodable audio and download a local WAV copy.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Choose an audio file up to 25 MB. The file stays in your browser.
  2. 2.Pick a speed from 0.5× to 2× after the audio has decoded. Faster or slower playback changes pitch too.
  3. 3.Select Change speed and export WAV, preview the result, then download the PCM16 WAV file.

About Audio Speed Changer

Audio Speed Changer creates a new speed-adjusted WAV file entirely in your browser. Choose an audio file your browser can decode, select a playback speed from 0.5× to 2×, then render and preview the result before downloading it. The selected file is decoded locally, routed through an offline audio renderer at the chosen rate, and exported as a fresh PCM16 WAV file. Nothing is uploaded to a server.

This is useful when you need a quick faster reference copy for a lecture, a slower practice version of a spoken clip, or a WAV handoff for another local editor. The result duration changes with the selected speed: 2× makes a one-minute source about 30 seconds long, while 0.5× makes it about two minutes long. The selected playback rate changes pitch together with duration; this is not pitch-preserving time stretching. The page reports the result duration and file size so you can check the outcome before downloading.

The download deliberately uses uncompressed PCM16 WAV for a clear, broadly readable local result. It does not preserve the source codec, bitrate, ID3 tags, artwork, chapters, or other embedded metadata, and it does not create an MP3. Browser codec support varies, so a file that your current browser cannot decode will show an error and no output file is created. For predictable browser memory use, input files are limited to 25 MB, 15 minutes, eight channels, 192 kHz, and 30 million rendered samples.

Methodology & sources

The browser decodes the complete local audio file, routes it through an OfflineAudioContext with the selected AudioBufferSourceNode playbackRate, then serializes the rendered channel frames as an interleaved little-endian PCM16 RIFF/WAVE file. Playback-rate rendering changes pitch with duration and is not pitch-preserving. The output is bounded before rendering and is not emitted when decoding or rendering fails.

Frequently asked questions

Can I change an MP3 file speed?
Yes when your browser can decode that MP3. The result is a new PCM16 WAV file, not an MP3, so the original MP3 compression and metadata are not retained.
Does changing speed preserve pitch?
No. This tool uses playback-rate rendering, so the pitch changes together with the duration. It is not a pitch-preserving time-stretching editor.
Are my audio files uploaded?
No. Decoding, offline rendering, previewing, and WAV creation run in your browser. The selected file is not sent to a server by this tool.
Why is the downloaded file larger than the original?
The download is uncompressed PCM16 WAV. Compressed formats such as MP3 or AAC can be much smaller, so a WAV copy commonly uses more storage even when it is shorter.

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