Does the audio pitch change when I speed up a video?

No. The audio is time-stretched with FFmpeg's atempo filter, so voices stay at their natural pitch instead of turning into chipmunk audio. You can also remove the audio entirely.

How long does speed changing take?

Processing runs on your device with FFmpeg.wasm, which is slower than real time. The first run also downloads the 32 MB FFmpeg core from Haivix R2; later runs reuse the browser cache.

Which speeds are available?

0.25×, 0.5×, 0.75×, 1.5×, 2×, 3×, and 4×. Faster and slower values are composed from chained atempo stages so the audio remains pitch-corrected.

Can I remove the sound completely?

Yes. Choose Remove audio and the output keeps only the video track. This is also selected automatically when the source has no audio.

Which formats can I use?

Inputs can be MP4, MOV, WebM, or MKV when FFmpeg can decode them. Output is MP4 with H.264 video and AAC audio for broad compatibility.

Change Video Speed Online — 0.25× to 4×

What Video Speed Changer helps you do

Speed up or slow down a clip from 0.25x to 4x while keeping the audio at its natural pitch. Faster playback is useful for tutorials and replays; slower playback helps with a physical technique or a hard-to-follow moment. You can also remove the sound entirely when the result is a silent study clip.

The video is decoded and encoded by FFmpeg running in your browser. No frame or audio sample is uploaded to Haivix.

How it works

The video is decoded and re-encoded at the new rate, while the audio is time-stretched with the atempo filter so voices do not turn into chipmunks. Extreme rates are composed from several atempo stages because a single filter stage has a limited range. The FFmpeg core runs in the browser through WebAssembly and is cached after the first download. Video and audio are processed together, so the two stay in sync at the new duration.

How to use Video Speed Changer

Load an MP4, MOV, WebM or MKV file.
Choose a speed between 0.25x and 4x.
Decide whether to keep or remove the audio.
Start the export and keep the tab open.
Wait for the FFmpeg core to load on the first run.
Preview the result and download the MP4.

When to use it

Compress a slow tutorial into a shorter review clip.
Study a sports or dance move at half speed.
Speed up a long screen recording of a repetitive task.
Create a timelapse-like result without a dedicated editor.
Remove audio and slow a clip for a visual reference.
Create a slow-motion reference for a sports technique.

When not to use it

Do not use 4x on content where every word matters.
Do not expect real-time processing; WebAssembly encoding is slower than playback.
Avoid very long clips on a low-memory device.
Do not speed up a recording that will be transcribed; the compressed speech is harder for speech recognition.

Example

A 20-minute software walkthrough is sped up to 2x for a review meeting, cutting it to about 10 minutes while the narration stays intelligible. The audio pitch is unchanged, so the presenter still sounds natural.

What you can do with Video Speed Changer

Choose 0.25x, 0.5x, 0.75x, 1.5x, 2x, 3x or 4x.
Keep pitch-corrected audio.
Remove the audio track entirely.
Export MP4 with H.264 video and AAC audio.
Reuse the cached FFmpeg core on later runs.
Pick a preset speed without typing a value.
Process the file locally, with no upload.

Example workflow

Trim before changing speed when only part of the clip needs the effect. Speeding up a 30-second section is much faster than processing an hour of footage.

If the result is for a platform with a length limit, check the new duration first. A 2x change halves the runtime but does not change the resolution, so the output can still be large.

For a study clip, slow the section down without audio and loop it beside the original. Keeping the original at normal speed makes it easier to compare what changed.

What to know before you start

Processing is slower than real time because it runs in WebAssembly.
The first run downloads a 32 MB FFmpeg core; later runs use the browser cache.
Extreme speeds can make fast motion hard to follow.
The output is MP4 with H.264/AAC, not the original container.
Very long or large files may exceed browser memory.

Common mistakes

Expecting the audio to stay identical at very high speeds.
Closing the tab during the first FFmpeg download.
Speeding up a clip that still needs frame-accurate trimming.
Forgetting that the output format changes to MP4.
Speeding up a clip that still has dead air at the start; trim it first.
Assuming a 2x speed change also halves the file size.

Troubleshooting

If the first run appears stuck, the FFmpeg core is still downloading. Leave the tab open and check the progress message.

If the audio sounds unnatural, try a less extreme speed. Time-stretching works best within a moderate range.

If the export fails on a large file, trim it first or process it on a desktop with more memory.

If the output stutters, the source may use a variable frame rate that the encoder normalised poorly. Convert it to a constant-frame-rate MP4 first, then change the speed.

If the output duration looks wrong, check the source frame rate; variable-frame-rate files can produce slightly different results.

Video Speed Changer