Video Speed Changer
Speed up or slow down any video with a single click
Drop a video file here or click to select
Video Speed Changer Features
Precise speed control for any video format
Quick preset buttons for common speeds: 0.25x, 0.5x, 1x, 1.5x, 2x, 4x and 8x.
Optional audio tempo adjustment keeps voices and music sounding natural at any speed.
Processing uses ffmpeg.wasm in the browser when the file, browser, and device support it.
Key Takeaways
- Speed changes use ffmpeg.wasm in the browser when the file, browser, and device support it.
- Keep Audio works cleanly only between 0.5x and 2x, where the atempo filter matches the tempo without pitch distortion; for 0.25x, 4x or 8x, uncheck Keep Audio to mute and avoid warped sound.
- Use the preset buttons for common speeds or type any positive value into the custom speed box for exact rates like 1.25x or 3x, then preview the result inline before downloading.
- Because encoding can use significant browser memory, use a desktop Chrome or Firefox with SharedArrayBuffer support and keep files modest in size, as very large clips can run out of memory or process slowly.
How to Change Video Speed in Your Browser
Add Your Video
Drag a video onto the drop zone or click Select Video to pick a file. The tool shows the name, size and duration once metadata loads. Browser-side processing is used when supported by the file, browser, and device.
Pick a Speed
Tap a preset button such as 0.5x, 1.5x, 2x or 4x, or type any positive value into the custom speed box for fine control. Leave Keep Audio checked to retain sound; uncheck it to mute the output, which is the cleanest option for extreme speeds.
Process and Download
Click Change Speed and wait while ffmpeg.wasm loads and re-encodes the video. When it finishes you can preview the result inline, then click Download Video to save it. The file keeps its original container and is named with the speed suffix, for example clip-2x.mp4.
How Speed Settings Affect Video and Audio
The tool changes timing with the FFmpeg setpts video filter and, when audio is kept, the atempo audio filter. The atempo filter only adjusts tempo cleanly within a 0.5x to 2x range, so behavior outside that window depends on whether you keep or mute the audio. Use this table to choose the right setting.
| Speed Setting | Video Effect | Audio With Keep Audio On | Best Use |
|---|---|---|---|
| 0.25x | Very slow motion | Outside atempo range, so leave audio off for a clean result | Detailed slow-motion review |
| 0.5x | Half speed | Tempo matched, pitch stays natural | Tutorials and language practice |
| 1x | Unchanged | Untouched | Re-encode without timing change |
| 1.5x | Faster playback | Tempo matched, voices stay natural | Lectures and long recordings |
| 2x | Double speed | Tempo matched at the upper atempo limit | Skimming long footage |
| 4x and 8x | Time-lapse style | Outside atempo range, so muting is recommended | Time-lapse and quick scrubbing |
Choosing the Right Settings
Keep Natural Sound
If you need intelligible speech or music, stay within 0.5x to 2x and leave Keep Audio checked. In this range the atempo filter matches the audio tempo to the new speed without the chipmunk or deep-voice effect.
Go Faster Than 2x
For 4x, 8x or higher, uncheck Keep Audio. Outside the 0.5x to 2x window the audio tempo is not corrected, so muting gives the cleanest silent time-lapse output.
Hit an Exact Speed
When a preset is not precise enough, type the value directly into the custom speed box. Any positive number works, so you can enter 1.25x, 1.8x or 3x to fine-tune the result.
Pick the Right Device
ffmpeg.wasm needs a modern browser with SharedArrayBuffer, so use desktop Chrome or Firefox for the most reliable processing. Keep source files modest in size since the whole job runs in browser memory.
Common Problems and Fixes
Audio sounds wrong at high or low speeds
The atempo filter only corrects audio between 0.5x and 2x. At speeds outside that range the audio is left unadjusted, so it can drift in pitch or sync. For 4x, 8x or 0.25x, uncheck Keep Audio to mute the output instead.
Processing failed or will not load
ffmpeg.wasm requires a browser that supports WebAssembly and SharedArrayBuffer. If you see a load or processing error, reload the page and try again in desktop Chrome or Firefox, and confirm your internet connection since the core files load on first use.
The page runs out of memory on large files
The entire video is read into browser memory and re-encoded, so very large files can exhaust available memory. Trim or compress the clip first, or work with shorter segments, then change the speed of each part.
Processing is slow
Because FFmpeg runs locally in WebAssembly rather than on a server, encoding time scales with video length, resolution and your hardware. Close other heavy tabs, use a desktop machine, and expect a short re-encode for longer or high-resolution clips.
How to Change Video Speed
Changing video speed is straightforward with our free online tool. Upload your video, select a speed multiplier, and download the processed video.
Frequently Asked Questions
Which video formats are supported?
The tool supports MP4, AVI, MOV, WebM, MKV and most other common video formats.
Processing uses ffmpeg.wasm which supports the same formats as desktop FFmpeg.
MP4 with H.264 encoding gives the best compatibility for the output file.
What is the fastest speed I can set?
The tool supports speeds from 0.1x (very slow) up to 16x (very fast).
Use the custom speed input to enter any value between these limits.
Extremely fast speeds (8x+) are useful for time-lapse style output.
Will changing speed affect audio?
With the audio option enabled, the audio tempo is adjusted to match the new speed.
This prevents the chipmunk effect at fast speeds and the deep voice effect at slow speeds.
The atempo filter works for speeds between 0.5x and 2x. Disable audio for other speeds.
Why does processing take a while?
ffmpeg.wasm can run FFmpeg in the browser using WebAssembly when supported.
Processing time depends on video length, resolution and your device's performance.
A 1-minute HD video typically takes 30-120 seconds depending on hardware.
Is there a file size limit?
Practical limits depend on file size, browser support, and available device memory.
Very large files (over 500MB) may exceed browser memory limits on some devices.
For best results, use files under 200MB.
Can I use this on mobile?
ffmpeg.wasm requires a modern browser with SharedArrayBuffer support.
Chrome on Android supports this. Safari on iOS may have limitations.
For mobile, use Chrome or Firefox for the best compatibility.
What happens to the audio at extreme speeds?
The atempo filter only supports 0.5x to 2.0x speed without quality loss.
For speeds outside this range, disable the audio option to mute the output.
Alternatively, the filter can be chained (e.g. 4x = two 2x passes) for higher speeds.
Is my video data private?
Completely private. Your video stays on your device.
browser-side workflows uses ffmpeg.wasm running locally in your browser.
No data is transmitted to any server at any point.
Sources and References
Format and tool details on this page are based on the official specifications and documentation below.
- Media container formats- MDN Web Docs
- FFmpeg documentation