NoCloud Media

Video tool

Video Speed Changer

Speed up or slow down any video. Audio keeps its pitch — no chipmunk effects.

How it works

  1. 1

    Drop your video

    MP4, MOV, WebM, MKV, AVI, or M4V. The file stays on your device.

  2. 2

    Pick a speed

    0.25x or 0.5x to slow down; 1.5x, 2x, or 4x to speed up. Audio pitch is preserved automatically.

  3. 3

    Convert in your browser

    We re-encode the video at a reasonable quality (H.264, CRF 23) and re-time the audio.

  4. 4

    Download the MP4

    Output is MP4 for broad compatibility regardless of the input container.

Why use Video speed changer?

Pitch-preserving audio — speeding up doesn't make voices sound chipmunky, slowing down doesn't make them sound muddy. The `atempo` filter handles this natively.

Private — your video never leaves your browser, which is handy for speed-adjusting personal recordings.

No watermarks, no size-limited free tier, no sign-up.

Common use cases

  • Slow down a tutorial video to catch every step
  • Speed up a long lecture recording to save time
  • Create a slow-motion effect from normal-speed footage
  • Make a fast-forward time-lapse from a long recording
  • Tighten a rambling video essay by running it at 1.5x
  • Match the pacing of a voice-over to B-roll

About MP4 and MP4

Changing playback speed means two things: re-timing the video frames (so they display faster or slower) and re-timing the audio (so it matches). The video side uses `setpts=PTS/N` to scale presentation timestamps, which requires re-encoding. The audio side uses `atempo`, which stretches or compresses audio without changing pitch. `atempo` is clamped to 0.5–2.0 per instance, so extreme speeds chain multiple instances — 4x becomes `atempo=2,atempo=2`, 0.25x becomes `atempo=0.5,atempo=0.5`.

Frequently asked questions

Is my video uploaded to a server?
No. NoCloud Media re-encodes your video entirely in your browser using WebAssembly. Your file never leaves this tab.
Will the audio pitch change?
No — pitch is preserved. We use FFmpeg's `atempo` filter, which stretches or compresses time without shifting frequency. Voices at 2x sound fast, not higher.
Why is the output re-encoded?
Changing playback speed changes presentation timestamps, which requires re-encoding the video stream. We use H.264 at CRF 23 for a quality/size balance that matches what most streaming services use.
Does this work on mobile?
Yes, but re-encoding is CPU-intensive; expect it to take several times longer on a phone than on a laptop.
What's the maximum file size?
It depends on your browser's available memory. Files up to 500MB work on most devices; files up to around 2GB may work on desktop with enough RAM.
Which browsers are supported?
Chrome, Edge, Firefox, and Safari 15+. We require WebAssembly and SharedArrayBuffer, both standard in modern browsers.

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