Is this video speed changer free?

Yes, completely free with no watermark, no signup, and no limits on video length.

Do my videos get uploaded to a server?

No. All processing happens in your browser using FFmpeg.wasm. Your videos never leave your device.

Can I slow down a video?

Yes, you can slow down to 0.25x (quarter speed) for smooth slow motion effects.

Can I speed up a video?

Yes, speed up to 4x. Great for timelapses, tutorials, or long recordings.

What happens to the audio?

You can keep the audio (pitch-adjusted to match the new speed), or remove it entirely.

What video formats are supported?

MP4, WebM, AVI, MOV, MKV and most common formats. Output is always MP4 (H.264).

Video Speed Changer

Change video playback speed — slow motion or speed up — then export as MP4. Preview in real-time, process entirely in your browser. No upload to any server, no watermark, completely free and private.

Drag & drop your video here

or browse files

MP4, WebM, AVI, MOV, MKV — max file size depends on your browser memory

Duration: — Resolution: — Size: —

Playback Speed

0.1x 4x

1.0x

Audio

Keep audio (pitch-adjusted) Remove audio

Original

—

Output

—

Time Saved

—

Preparing...

How the Video Speed Changer Works

This video speed changer uses two technologies working together to give you real-time preview and high-quality export. When you load a video, the HTML5 Video API applies the speed change instantly for preview using the playbackRate property. This lets you hear and see the result immediately without waiting for any processing. When you are ready to export, FFmpeg.wasm — a full-featured video encoder compiled to WebAssembly — re-encodes the video at the selected speed using professional-grade filters like setpts for video timing and atempo for audio tempo adjustment.

All processing happens entirely in your browser. Your video file is never uploaded to any server. The file stays in your device memory during processing, and the exported result is downloaded directly to your computer. This makes the tool suitable for confidential footage, personal videos, and any content you do not want leaving your device.

Speed Change Use Cases

Slow motion is valuable for sports analysis, dance choreography review, nature footage of fast-moving subjects, and educational demonstrations where step-by-step detail matters. Setting the speed to 0.25x or 0.5x reveals details invisible at normal playback. Speed up is ideal for timelapses from security cameras or dashcams, compressing long tutorials into shorter summaries, and creating fast-forward effects for social media content. A 2x to 4x speed turns a 10-minute walkthrough into a quick overview.

Audio Handling and Pitch Correction

When you change video speed, audio pitch naturally shifts — faster playback raises pitch (chipmunk effect) while slower playback lowers it. The "Keep audio (pitch-adjusted)" option uses the atempo filter in FFmpeg, which adjusts audio tempo while preserving the original pitch. This means voices sound natural even at 1.5x or 2x speed. For extreme speed changes below 0.5x, the filter chains multiple atempo stages to maintain quality. If you do not need audio — for example, when creating a timelapse with background music added later — select "Remove audio" for a smaller file and faster export.

Tips for Best Results

For smooth slow motion, start with video filmed at 60fps or higher. Slowing down 30fps footage to 0.25x can look choppy because there are not enough frames to fill the extended duration. For speed-up effects, any frame rate works well since frames are being dropped rather than interpolated. Keep in mind that very large video files (over 1GB) may take significant time to process in the browser. If export is slow, try trimming the video first or reducing resolution. The output format is always MP4 with H.264 encoding, which is compatible with virtually every device and platform including YouTube, Instagram, TikTok, and all major video editors.