UtilityKit

500+ fast, free tools. Most run in your browser only; Image & PDF tools upload files to the backend when you run them.

Video Speed Changer

Speed up or slow down any video from 0.25x to 4x with optional pitch preservation and reverse playback.

About Video Speed Changer

Video Speed Changer lets you speed up or slow down any video from 0.25x (slow motion) all the way to 4x (time-lapse), with full control over audio pitch preservation and optional reverse playback. All processing happens in your browser via ffmpeg.wasm — your video file is never uploaded. The tool chains ffmpeg's atempo audio filter to handle speeds outside the 0.5–2x range without distortion: for example, 4x speed uses two atempo=2 filters in series. The pitch preservation toggle keeps voices and music sounding natural at any speed. The reverse option loads the full video into memory for a frame-reversal pass.

Why use Video Speed Changer

  • 100% private — video never leaves your device
  • Speeds from 0.25x slow-motion to 4x time-lapse
  • Pitch preservation for natural-sounding audio at any speed
  • Custom speed input for precise fractional values
  • Reverse option for creative effects
  • No watermarks, no signup, free to use

How to use Video Speed Changer

  1. Upload your MP4, WebM or MOV video.
  2. Click a speed preset chip (0.25x to 4x) or type a custom speed in the text field.
  3. Toggle 'Preserve audio pitch' on to keep audio natural at non-1x speeds.
  4. Toggle 'Reverse video' to flip the video and audio in time.
  5. Click 'Process Video' and wait for ffmpeg.wasm to render.
  6. Preview and download the result.
  7. Watch the progress meter — long clips and reverse mode take longer.

When to use Video Speed Changer

  • Creating slow-motion highlights from sports or action footage
  • Making time-lapse sequences from longer recordings
  • Speeding up tutorial recordings to save watch time
  • Reversing a clip for a creative video effect
  • Reducing the runtime of a long lecture without losing legibility
  • Stretching a quick phone clip into a hero slow-mo moment

Examples

1.5x tutorial speed-up

Input: 10-min MP4 tutorial, 1.5x speed, pitch preserved

Output: Around 6 min 40 sec MP4 with intelligible natural-sounding speech

0.5x slow-mo highlight

Input: 5-second 60 fps MOV action clip, 0.5x speed, pitch preserved

Output: 10-second slow-motion MOV with smooth motion and natural audio

4x time-lapse

Input: 2-min WebM landscape capture, 4x speed, audio chained atempo

Output: 30-second WebM time-lapse with chained atempo audio that stays clean

Tips

  • For tutorial speed-ups, 1.5x with pitch preservation usually keeps speech fully intelligible while shaving 33% off the runtime.
  • Slow motion below 0.5x can look choppy if the source is 30 fps — for smooth slow-mo, start from 60 fps source footage.
  • Disable pitch preservation for stylised effects (chipmunk voice, deep slow-mo) — it's a deliberate creative choice rather than a bug.
  • Reverse mode is memory-heavy because it loads the whole clip into RAM. Trim long sources first with the Video Trimmer.
  • For time-lapse from a slow scene (clouds, traffic), 4x with audio muted often looks best — add music in a separate editor.
  • Custom speeds like 1.25x can subtly tighten pace in vlogs without viewers noticing the change.

Frequently Asked Questions

Does my video leave my device?▾
No, processing is 100% local in your browser. Your video is never uploaded to any server.
What does pitch preservation do?▾
Without pitch preservation, speeding up a video raises the audio pitch and slowing it down lowers it. With pitch preservation enabled, the atempo filter corrects for this so voices and music sound natural.
Why does 4x speed chain two atempo filters?▾
The ffmpeg atempo filter only accepts values between 0.5 and 2. For speeds outside that range the tool chains multiple filters in series to reach the target speed without distortion.
Why does reverse take longer?▾
Reversing requires reading every frame of the video into memory and writing them back in reverse order. For large files this is significantly slower than forward-speed changes.
Can I enter a fractional speed like 1.75x?▾
Yes, type any decimal value into the custom speed field. The chip buttons will deselect automatically.
What video formats are supported?▾
MP4, WebM and MOV. The output format matches the input container.
Why does it need SharedArrayBuffer?▾
ffmpeg.wasm uses SharedArrayBuffer for multi-threaded encoding. It is only available on cross-origin-isolated (COOP/COEP) pages in Chromium-based browsers.
Is there a maximum file size?▾
There is no server-side limit because nothing uploads. Browser memory is the practical ceiling — most laptops handle 1–2 GB; reverse mode on huge files can be slower or fail on low-RAM devices.

Explore the category

GIF Speed Changer Speed up or slow down any animated GIF using a precise multiplier. setpts filter via ffmpeg.wasm — palette-aware, browser-only, no upload. Audio Speed & Pitch Changer Speed audio up or slow it down without changing pitch, or shift pitch in semitones independently of speed. MP3, WAV, M4A, OGG, FLAC. ffmpeg.wasm in browser. Video Trimmer Cut and trim MP4, WebM, MOV videos to exact start and end times, right in your browser. Video to GIF Converter Convert MP4 and WebM video clips into smooth, optimised GIF animations with two-pass palette rendering. Video Resize & Converter Resize video to 1080p, 720p, 480p or 360p and convert between MP4 and WebM with adjustable CRF quality. Video Frame Extractor Extract single frames or batch screenshots from any video at precise timestamps or regular intervals. Download as PNG, JPG, or ZIP.
MP4 and H.264 Explained: How Modern Video Compression Works An MP4 is just a wrapper. The real magic is the codec inside. We unpack containers, codecs, B-frames, and why H.264 is still everywhere desp May 2026 · 9 min GIF vs WebP vs MP4: Which Animation Format Wins on the Web? Animated GIFs are nostalgic but heavy. WebP and MP4 deliver the same motion at a fraction of the size. We compare file size, browser support May 2026 · 9 min

Glossary

ffmpeg.wasm
WebAssembly build of FFmpeg that runs the full speed/reverse pipeline in the browser without any server processing.
SharedArrayBuffer
Multi-threading shared memory required by ffmpeg.wasm. Available only on cross-origin-isolated (COOP/COEP) pages.
atempo filter
FFmpeg audio filter that changes playback tempo while preserving pitch. Each instance accepts 0.5–2.0; chain multiple to reach larger factors.
setpts filter
FFmpeg video filter that rescales presentation timestamps to speed up or slow down the video stream itself.
Codec
The compression algorithm (H.264, VP9) used to encode the output. The tool re-encodes during speed changes.
Container format
The MP4/WebM/MOV wrapper that the output is written into. Matches the input container.
Frame rate (FPS)
Frames per second of the source. Slow-motion looks smoother when the source has high FPS (60 or higher).
Two-pass encoding
Encoding strategy where the encoder first analyses content, then produces output. Not used here, but relevant for size-targeted exports.