Skip to main content

Change audio speed online

Speed up or slow down audio with real-time preview, pitch preservation, and waveform display.

Free & unlimited
All processing happens in your browser. No data is sent to any server.

Make a recording play faster or slower and save the result as a file, rather than just changing a player's playback speed. The decoded audio is rendered through an OfflineAudioContext at a new playback rate, which is the same mechanism as running a tape at the wrong speed: pitch rises when you speed up and falls when you slow down. Preset speeds run from 0.25x to 3x, and six use-case presets cover podcast review at 1.5x, lecture speed at 1.75x, music practice at 0.75x, transcription at 0.5x, audiobook at 1.25x and time-lapse at 4x. The new duration is shown before you render, and the output is a WAV whose filename records the rate you used.

Key facts about Change audio speed online

Key facts about Change audio speed online
MechanismResampling: the source buffer is rendered at a new playbackRate inside an OfflineAudioContext
ConsequencePitch moves with speed. At 2x everything is an octave higher; at 0.5x an octave lower
Speed presets0.25x, 0.5x, 0.75x, 1x, 1.25x, 1.5x, 2x and 3x, plus a 4x time-lapse use case
Use-case presetsPodcast review 1.5x, lecture 1.75x, music practice 0.75x, transcription 0.5x, audiobook 1.25x, time-lapse 4x
Output lengthOriginal duration divided by the speed factor, shown before you render
Output16-bit PCM WAV with the speed factor in the filename, such as -1.5x
Sample rateThe source's own rate is kept; the content is resampled into it
Live previewPreview playback uses the same rate, so what you hear is what renders
Accepted inputMP3, WAV, OGG, FLAC, AAC and M4A, up to 500 MB

What happens to your file

Nothing is uploaded and no processing engine is downloaded. Your file is read into an ArrayBuffer inside this tab, decoded by the browser's own decodeAudioData, re-rendered through an OfflineAudioContext on your CPU, and written back as a 16-bit WAV by JavaScript on this page. After the page loads, changing a file's speed produces no network request whatsoever — an empty Network panel during a render confirms it. The download is a blob: URL pointing at memory in your own tab, released when you close the page.

About this tool

  1. 1

    Load the file

    Drop an MP3, WAV, OGG, FLAC, AAC or M4A up to 500 MB. Duration, channels and sample rate appear once it has decoded.

  2. 2

    Pick a speed

    Tap one of the preset rates from 0.25x to 3x, or pick a use case — podcast review, lecture, music practice, transcription, audiobook or time-lapse — which sets the rate for you.

  3. 3

    Check the new duration

    The page shows what the output will be before you render, so you can see whether 1.5x actually gets a 70-minute recording down to the length you need.

  4. 4

    Preview

    Play it at the chosen rate first. Speech stays intelligible well past 1.5x; music at anything above about 1.25x starts to sound comic because the pitch rises with it.

  5. 5

    Render

    The whole file is rendered offline in one pass, much faster than real time even at 0.25x.

  6. 6

    Download the WAV

    The filename records the rate. Convert it to MP3 with the audio converter if you want to put it on a phone.

Specs & compatibility
Input formatsMP3, WAV, OGG, FLAC, AAC, M4A
Maximum file size500 MB
Speed range0.25x to 4x
Output format16-bit PCM WAV
Output durationOriginal seconds divided by the speed factor
PitchChanges with speed by the same ratio — this is resampling, not time-stretching
BrowsersChrome, Edge, Firefox and Safari 14.1+ — Web Audio only, no WebAssembly
Speed of processingOffline rendering runs far faster than real time regardless of the chosen playback rate
  • Pitch rises with speed here. If a voice sounding higher bothers you, stay under about 1.25x, where the shift is small enough to ignore.
  • For slowing music down to learn a part, 0.75x keeps it musical; 0.5x drops it a full octave, which makes the notes hard to relate to the original.
  • Transcription at 0.5x works well precisely because the pitch drop makes words easier to separate, even though it sounds odd.
  • Speeding up is the cheapest way to make a long meeting recording listenable, and it does not lose any content the way silence removal does.
  • If your goal is a shorter file without a pitch change, remove the pauses instead — that shortens speech without touching the audio you keep.
  • The result is a WAV and therefore large, but slowing down makes it larger still, since duration grows in the same ratio.
  • Combine with the pitch shifter only if you understand that both tools resample: applying one after the other multiplies the effects.
  • Speeds from 0.25x to 4x
  • Eight preset rates and six use-case presets
  • New duration calculated before you render
  • Live preview at the selected rate
  • Whole-file offline rendering
  • 16-bit WAV output at the source sample rate
  • Getting through a two-hour meeting recording at 1.5x without a player that supports it
  • Slowing a guitar solo to 0.75x to work out the notes
  • Producing a 0.5x copy of an interview for manual transcription
  • Speeding up a long field recording to scan for the interesting parts
  • Making an audiobook chapter play at a comfortable 1.25x on a device with no speed control
  • Creating a time-lapse audio bed at 4x to sit under a sped-up video
Yes. This tool changes speed by resampling — the decoded audio is rendered back at a different playback rate — which is the same thing that happens when a record plays at the wrong speed. Doubling the speed raises the pitch by an octave; halving it lowers the pitch by an octave. Keeping pitch constant while changing tempo requires a phase vocoder or a granular time-stretch algorithm, which is a different and much heavier piece of processing than what runs here.
Exactly the original duration divided by the speed factor. At 1.5x a 60-minute recording becomes 40 minutes; at 2x it becomes 30; at 0.75x it grows to 80. The page calculates and displays this before you render, so you can check whether the rate you picked actually hits the length you need. Note that this is a uniform change: unlike removing pauses, nothing is cut, so every word and every gap is still present, just compressed in time.
For speech, 1.5x is the common sweet spot and the podcast review preset uses it — most listeners adapt within a minute and comprehension holds up. The lecture preset goes to 1.75x, which suits slow, deliberate speakers. Beyond 2x intelligibility drops sharply for most people, and the pitch shift that comes with resampling makes it harder still. Going the other way, 0.5x is the transcription preset: slow enough to catch every word, at the cost of sounding an octave low.
16-bit PCM WAV, at the source's own sample rate, with the rate written into the filename. WAV is used because it is the only lossless container a browser can write without an external encoder, so this step adds no compression artefacts of its own. The trade is size: roughly 10 MB per stereo minute at 44.1 kHz, and slowing a file down makes it proportionally larger. Run the result through the audio converter if you need MP3 or AAC for a phone or a podcast host.
Up to 500 MB, which covers several hours of MP3. There is no WebAssembly heap constraining this tool the way there is in the converters, because it uses only the Web Audio API. The real limit is device memory: the decoded source and the rendered result are both held as 32-bit float buffers, so an hour of stereo audio can occupy a couple of gigabytes while you work. On mobile the browser will usually reclaim the tab well before you reach the nominal file cap.
No. This tool uses nothing but the Web Audio API built into your browser: the file is decoded in the tab, rendered through an OfflineAudioContext on your own CPU, and written back to WAV by JavaScript on this page. It does not even download a processing engine, so unlike the converter tools here there is no network activity at all once the page has loaded. The result is a blob: URL in your tab's memory, and it disappears the moment you close or reload.

Related tools

View all

Part of Audio tools that run in your browser

Updated

We use anonymous analytics to improve ToolChamp. No personal data is stored or sold. Privacy Policy