Can I make an MP4 slow motion?

Yes. Open Speed Video, choose a speed below 1x, preview the playback, and export a new MP4.

Is the video uploaded?

No. The linked speed editor processes the selected file in your browser.

Will audio stay in sync?

The speed tool adjusts the output timing and uses FFmpeg audio handling to keep the exported MP4 aligned.

Slow motion

Slow Motion Video Online

Turn a clip into slower motion for tutorials, highlights, reactions, or timing checks while keeping the source file on your device.

Make slow motion Trim first

Choose a slow-motion speed that fits the footage

Reducing playback speed lengthens the timeline. The right setting depends on whether you want a subtle emphasis, a tutorial pace, or close inspection of fast action.

Use speed as a storytelling choice

A 0.75x setting creates a mild slowdown, 0.5x doubles the approximate duration, and 0.25x makes the result roughly four times as long. Strong slowdown cannot invent motion detail that the camera did not capture, so low-frame-rate sources may look stepped.

Try 0.5x for highlights and clearly visible actions.
Use 0.25x for inspection rather than guaranteed smooth motion.
Trim to the important moment before creating a very long result.

Review motion and audio together

Changing speed also changes the timing of the soundtrack. The export pipeline keeps the media timeline aligned, but heavily slowed speech and music can sound unnatural. Preview the final MP4 and consider removing or replacing audio when the visual effect matters more.

Check the full duration after export.
Listen for audio artifacts at aggressive speed changes.
Use Mute Video when a silent slow-motion clip is preferable.

How it works

Three steps to finish the browser workflow.

1
Choose a video
Open Speed Video and select the clip you want to slow down.
2
Pick a slower speed
Choose 0.75x, 0.5x, 0.25x, or set a custom speed in the editor.
3
Export slow motion
Preview the timing, then export and download the slower MP4.