Audio Speed Changer

Audio Speed Changer makes audio faster or slower while keeping its pitch. Choose a preset from 0.5× to 2× or any custom speed from 0.25× to 4×, see the expected new length, and save the result as MP3, WAV, FLAC, Ogg Vorbis or Opus. Time stretching uses FFmpeg’s atempo filter in libav.js, an open-source WebAssembly build of FFmpeg’s libraries loaded from this site, running in your browser.

Speeding up lectures and podcasts saves time; slowing down music or language lessons makes them easier to follow. Simply changing the playback rate also changes the pitch, while a time-stretch filter keeps voices natural. Large changes — below 0.5× or above 2× — use several filter passes and can sound less natural.

1. Drop an MP3, WAV, FLAC, Ogg, Opus or WebM audio file onto the upload area.
2. Listen to the original and check its length.
3. Pick a speed preset or type a custom speed between 0.25× and 4×.
4. Check the expected output length shown under the speed.
5. Choose the output format and bitrate.
6. Press Change speed, listen to the result and download it.

• Pitch-preserving speed change with FFmpeg’s atempo filter
• Presets for 0.5×, 0.75×, 1×, 1.25×, 1.5× and 2×
• Custom speeds from 0.25× to 4× with validation
• Original and expected output length shown before processing
• Multi-pass processing for very slow or very fast speeds, clearly noted
• MP3, WAV, FLAC, Ogg Vorbis and Opus output
• Real progress and a Stop button
• Runs locally — nothing is uploaded

• Use 1.25×–1.5× for speech; most listeners still understand it easily.
• Use 0.75× for practising music or language listening.
• Avoid extreme speeds for music — artefacts become audible.
• Choose WAV or FLAC if you will process the audio again.
• Listen to the result before replacing the original.