Change Video Speed Online

Create smooth slow-motion highlights or fast-forward timelapses without opening a timeline editor. Choose a speed multiplier — 0.5× for dramatic slow-motion, 2× for accelerated walkthroughs, or custom values in between — and export a new MP4 with the adjusted duration and pitch-corrected or natural audio.

Speed changes run locally in the browser tab through FFmpeg WebAssembly. Sports footage, tutorial recordings, product demos, and creative social content all process on your device — no upload, no account, and no waiting in a cloud render queue.

How to change video speed online

1

Upload your clip

Shorter clips encode faster — trim first if the speed change only applies to part of the footage. MP4 and MOV work best. Drop the file onto the upload zone.

2

Select the speed multiplier

Choose from common presets: 0.25× (quarter speed slow-motion), 0.5× (half speed), 1.5× (slightly accelerated), 2× (double speed), or a custom value supported by the tool.

3

Preview the audio impact

Consider the audio result at your chosen speed. Speech at 2× sounds chipmunk-like. Slow motion below 0.5× deepens pitch significantly. Decide if you want to mute and add replacement music.

4

Process locally

FFmpeg adjusts the PTS (presentation timestamps) for the video frames and applies audio tempo stretching. The output duration changes proportionally to the speed factor.

5

Download and verify

Check the motion feels natural for the effect you intended. Check the total duration is within platform length limits — faster clips are proportionally shorter.

Common use cases

  • Sports and fitness highlights

    Slow key moments — a tennis serve, a gymnastic dismount, a weight-lift lockout — to 0.5× for Instagram analysis reels and coaching feedback.

  • Tutorial and workflow acceleration

    Developers, designers, and chefs speed up repetitive or slow preparation segments before uploading to YouTube — viewers get the context without waiting through tedious real-time steps.

  • Timelapse and construction documentation

    A 10-minute plant growth clip or building construction walkthrough becomes a watchable 2-minute timelapse at 5× speed — no specialist timelapse app required.

  • Comedy timing edits

    Fast-forward through boring setups and slow-motion punchlines for meme video formats where speed contrast is the visual punchline.

  • Product demo acceleration

    E-commerce brands speed up unboxing or setup sequences to show the full assembly process in 30 seconds rather than 3 minutes.

  • Music synchronisation

    Slightly adjust clip speed (1.05×–1.15×) to match a video's duration to a music track length without cutting content.

Best practices

  • For silky smooth slow motion, start with 60 fps source footage — 30 fps at 0.5× can look choppy because there are not enough source frames to fill the slowed playback.
  • Mute audio before slowing to extreme speeds (below 0.5×) or accelerating above 2× when the pitch-shifted audio sounds unnatural.
  • Trim to the exact segment that needs the speed change and recombine with the Combine Videos tool — applying different speeds to different segments produces the most professional result.
  • After a 2× speed change, check the output duration — a 60-second clip becomes 30 seconds. Confirm this is within your target platform's length requirements.
  • Export from the original source file each time; chaining multiple speed changes in successive passes accumulates quality degradation.
  • For slow motion where you need frame interpolation (smoother 120 fps-style motion), a desktop tool like CapCut or DaVinci Resolve provides optical flow, which this browser tool does not.

Formats & compatibility

Outputs MP4 (H.264 + AAC). Supported speed range is typically 0.25×–4× (varies by UI). Audio is time-stretched proportionally with the video; extreme factors may sound unnatural on speech-heavy content. Processing is entirely client-side.

Related tools

  • Reverse video — pair reversal with speed changes for creative trend edits
  • Mute video — remove pitch-shifted audio and add fresh music after the speed change
  • Video trimmer — isolate the exact segment to speed up or slow down

Pick your speed factor above and download a paced MP4 ready to post — free and private.

Frequently asked questions

0.5× halves the speed. 0.25× (quarter speed) is typically the practical minimum in-browser — lower factors on 30 fps footage produce visible stutter between frames because the source does not contain enough frames for smooth interpolation.
Audio is time-stretched with the video. Speech at 2× sounds sped up but intelligible; at 4× it sounds like fast-forward. For sped-up tutorials, many creators mute and add upbeat background music instead.
One encode pass at a reasonable bitrate preserves detail well. Very high speeds on low-frame-rate sources look jumpy, but that is a source material limitation, not a quality loss from compression.
Yes on capable desktops. 4K speed changes take longer to process locally — expect several minutes for clips over 5 minutes long.
This tool offers quick single-factor speed changes in-browser with no installation. For complex variable speed ramps, optical flow slow motion, or per-clip speed on a timeline, a full NLE like DaVinci Resolve or Final Cut Pro is the right tool.
No. Speed adjustment runs entirely in the browser — no file ever leaves your device.
Yes. A 60-second clip at 2× produces a 30-second output. A 60-second clip at 0.5× produces a 120-second output.
Trim to each segment, apply the appropriate speed to each, then recombine them with the Combine Videos tool to create a clip with different speeds in different sections.