Audio Speed Changer

About changing the speed of audio

Some recordings are too slow to sit through and some are too fast to follow. Both are fixable, and it takes seconds.

Slow a lecture to 0.75x and you can actually take notes. Speed a podcast to 1.5x and an hour becomes forty minutes. Drop a guitar solo to 0.5x and you can hear every note in it. Slow an interview down and you can type along without pausing every five seconds.

Your player can do this while you listen. This makes a file that is actually changed, so it plays at the new speed anywhere — in a car, on an old MP3 player, in an app with no speed control, or on a phone with the screen off.

The voice still sounds like a voice

Change the speed of a tape and the pitch goes with it. That is why sped-up voices sound like chipmunks.

This tool does not do that by default. Keep it natural changes how fast the words arrive without changing the voice saying them, so a lecture at 1.5x sounds like someone talking briskly rather than a cartoon. That is what you want for speech, nearly always.

Let it rise and fall is the opposite, on purpose. It moves the pitch with the speed, the way a tape or a record does. Choose it when that effect *is* the point — a deep slowed-down sample, a sped-up novelty clip, or a track you want to shift in key.

Choosing the speed

Tap one of the presets — 0.5x, 0.75x, 1.25x, 1.5x, 2x — or type any value between 0.25 and 4.

The New length box updates as you choose, so you can see what a 52-minute recording becomes before you commit to it. The player above also follows your choice, so you can hear roughly how it will sound first.

Speeds far from 1x are applied in steps rather than in one jump, which is what keeps the sound clean. Beyond about 2x speech gets hard to follow no matter how well it is processed — that is your ears, not the tool.

Everything happens on your device

The engine is a real audio toolchain (ffmpeg) compiled to WebAssembly and run inside your browser. Your file is never sent anywhere:

• Private — a recorded lecture, an interview, a client's audio stays yours
• No upload wait — a long recording starts immediately
• No file size limit imposed by an upload
• No sign-up, no watermark, no queue

The engine is about 30 MB and downloads once. Your browser keeps it afterwards, so the second file starts straight away — even offline. The work runs in the background, so you can switch tabs while a long file processes; just keep this one open.

What people use it for

• Slowing a lecture or a language lesson down to a pace you can follow
• Speeding up a podcast or an audiobook to get through it
• Slowing music down to learn a part note by note
• Slowing an interview down to transcribe it without constant pausing
• Speeding up a voice memo you already know the gist of
• Fitting a voiceover to the length of a video
• Making a track longer or shorter to match something else

Good to know

• Works with MP3, WAV, M4A, OGG and FLAC, and saves as MP3, WAV or M4A
• Changing the speed re-encodes the audio, so save as WAV if you plan to edit it afterwards
• A slower file is a longer file, and a faster one is shorter — the file size follows
• Speed cannot add detail that was never recorded; a poor recording slowed down is still a poor recording
• To change the speed of a video, use Change Video Speed
• To cut the file down first, use Audio Trim

How to use it

• Click Click to upload, or drag an audio file onto the box
• Pick a speed preset, or type your own between 0.25 and 4
• Leave Keep it natural on for speech; switch to Let it rise and fall for a tape effect
• Choose the output format — MP3 for anywhere, WAV if you will edit it next
• Press Change the speed, play the result, then Download audio

Related tools

• Change Video Speed — the same idea, for video
• Audio Trim — cut the part you need before or after
• Audio Converter — change the file format
• Audio to Text — transcribe the recording instead
• Remove Background Noise — clean a noisy recording
• Voice Recorder — record something new first