Speed up or slow down a video
Pick a speed from 0.25x to 4x and download. Audio stays in sync and at its natural pitch, so a 2x tutorial still sounds like a person, not a chipmunk. Processing runs on your device in the browser; nothing is uploaded.
Runs in your browser with ffmpeg. The file is never uploaded.
About the video speed changer
Changing the speed of a video is two jobs that have to agree with each other. The picture side is easy: the frame timestamps are scaled, so a 2x clip shows each frame for half as long. The audio side is where cheap tools fail. Simply playing the audio faster raises its pitch, which is the chipmunk effect; slowing it drops the pitch to a growl. This tool uses a time-stretch filter that changes tempo while preserving pitch, the same class of algorithm podcast apps use for 1.5x playback, and chains it in stages for large changes so 0.25x and 4x stay clean. The result is speech that is faster or slower but still sounds like the speaker. Speeding up is the everyday use: a 10-minute screen recording at 2x becomes a 5-minute tutorial that people actually finish, and a long time-lapse at 4x. Slowing down is for analysis and effect: sports form, a dance move, a product reveal at 0.5x. Frame rate stays the same, so slow motion at 0.25x repeats frames rather than inventing new ones; true slow motion needs footage shot at a high frame rate. Everything runs in the browser with ffmpeg compiled to WebAssembly, so no upload and no watermark.
How it works
Drop your video
MP4, MOV, WebM or MKV, up to 500MB. It is processed in your browser with ffmpeg, nothing is uploaded anywhere.
Pick the settings
Times, quality, size or speed depending on the tool. A progress bar shows how far along the export is.
Download
The result saves to your device. Free, no watermark, no signup.
Tips for best results
Things that meaningfully improve the output.
1.5x to 2x for tutorials and lectures
Speech stays fully intelligible with pitch preserved. Above 2x, listeners start to miss words; use it for time-lapses and B-roll.
Slow motion needs frame rate
A 30 fps clip at 0.25x shows each frame four times. It looks fine for analysis; for cinematic slow-mo, record at 120 or 240 fps first.
Trim first
Speed changes re-encode the whole clip. Cut it down to the useful part with the trimmer and the export takes a fraction of the time.
Check music
Pitch-preserved tempo change works well on speech. On music it can introduce slight artifacts at extreme settings; 0.75x to 1.5x are safe.
Need more than video speed changer?
renza turns photos into video with Kling, Veo and Seedance, and upscales footage to 4K. Free credits at signup, no credit card.
Create free account →Frequently asked questions
Will the voice sound like a chipmunk?
No. The audio is time-stretched with pitch preserved, so speech keeps its natural tone at every speed.
What speeds are available?
0.25x, 0.5x, 0.75x, 1.25x, 1.5x, 2x, 3x and 4x. Intermediate values are rarely needed and those cover tutorials, time-lapses and slow-motion review.
Is my video uploaded?
No. The whole process runs in your browser with ffmpeg compiled to WebAssembly.
Does the audio stay in sync?
Yes. Video and audio are scaled by the same factor in a single pass, so they stay locked together.
Does it work on a video with no sound?
Yes. The tool detects a missing audio track and processes the picture only.