Report Bug / Feature Request
AI Video Generator AI Video Editor AI Video Enhancer AI Video Dubbing Studio AI Performance Capture (Runway Act-Two) AI Video Translator AI Video Effects — Pikaffects-style AI Video Upscaler More →

AI Slow Motion

Commercial use OK 380+ models No watermark No sign-up needed
Model:
+ GPT-5, Claude, Gemini
Drop a video and pick a slow-motion factor. With FPS interpolation ON (the default), we render true intermediate frames with motion compensation — the smooth slow-mo look you see on sports replays. Without it, duplicate frames are inserted (fast but choppy).

Drag a video here or click to upload

MP4, MOV, WebM, MKV up to 200MB — shorter clips finish faster with interpolation

— — — —
ON — ffmpeg minterpolate generates intermediate frames with motion compensation. Silky smooth but slow: expect 2-5× realtime on the GPU.
Higher = smoother slow-mo, longer render. Only used with FPS interpolation.
Output duration preview
—
—
rendered output length
Token estimate for your clip
—
Buy tokens
Upload a video to see the exact cost for your clip.
Original (normal speed)
Slow motion
Download

Footage types that slow-mo well

Sports replays

Goals, dunks, serves. 4× with interpolation + 60fps output is the sweet spot for feet-leave-floor drama.

Splash & explosion shots

Liquid, dust, fireworks, confetti. Motion interpolation shines on high-frequency chaotic motion.

Product reveals

Unboxings, reveals, product spins. 2× gives a premium feel without dragging the pacing.

4-step how-to

  1. Upload your clip. We read duration + dimensions and preview the output length at your chosen slow-mo factor.
  2. Pick 2× / 4× / 8× slower. Leave FPS interpolation ON for smooth motion, OFF for the naive (cheap, fast) path.
  3. Pick an output frame rate — 60fps is a good default. 120fps is cinematic but doubles render time.
  4. Hit Apply. Interpolation at 4× on a 60s clip takes 3-5 minutes — close the tab and we'll email when it's done.

vs. Twixtor, Flowframes, DaVinci Optical Flow

Twixtor is the plugin pros use inside After Effects at $330 — the motion tracking is still the cleanest. Flowframes is free on Windows but needs a local GPU and a few minutes per clip. DaVinci Resolve Studio ships Optical Flow (Speed Warp) — great, but requires the $295 paid tier. This tool uses ffmpeg minterpolate — same motion-compensated interpolation primitive Twixtor builds on — in a browser tab. Output is frame-for-frame comparable on most clips; the pro tools edge ahead on extreme motion or tight closeups.

When NOT to enable interpolation

  • Already-240fps or 120fps high-speed camera footage — the frames are real, no need to synthesize. Just setpts.
  • Heavy motion-blur in source — interpolation amplifies the blur smear. Skip it or lower to 2×.
  • You're on a budget — 4× interpolation on a 60s clip is 12K tokens vs 3K for naive. Naive is fine for context / background B-roll.
Advanced options
Result
Tokens running low. Get More Tokens
Want better results? Premium models (GPT-5, Claude, Gemini) deliver higher quality. View Plans

❤️ Love Free.ai? Tell your friends!

Sign up to get a referral link and earn 25,000 tokens per friend.

Want more? Sign up free for 5K tokens/day + 10K bonus
Sign Up Free

Processing your request...

Turn any video into smooth slow motion. 2x / 4x / 8x slower with ffmpeg minterpolate motion-compensated frame synthesis. Free inside your token pool.

How to Use AI Slow Motion

1
Enter your input

Type text, upload a file, or describe what you want. No account needed.

2
Click generate

Our AI processes your request in seconds using the best open-source models.

3
Download & share

Download, copy, or share your result. Free for personal and commercial use.

Use this tool via API

Automate this tool from your own code. OpenAI-compatible REST endpoint, Bearer-token auth, no extra SDK required. Token costs match the web interface.

API Documentation Get API Key 
curl -X POST https://api.free.ai/v1/video/generate/ \
  -H "Authorization: Bearer sk-free-..." \
  -H "Content-Type: application/json" \
  -d '{"prompt": "A cat playing piano", "duration": 4}'

Related Free AI Tools

AI Video Generator
AI Video Editor
AI Video Enhancer
AI Video Dubbing Studio
AI Performance Capture (Runway Act-Two)
AI Video Translator
AI Video Effects — Pikaffects-style
AI Video Upscaler

AI Slow Motion — FAQ

Time-remaps a video to 2×, 4×, or 8× slower. With FPS interpolation ON (the default), ffmpeg minterpolate generates true intermediate frames with motion compensation — the smooth slow-mo sports-replay look. With it OFF, duplicate frames are inserted (choppy but fast and cheap).

Motion-compensated frame interpolation analyzes adjacent frames, estimates pixel motion, and synthesizes intermediate frames that follow that motion. Without it, stretching a 60fps clip to 4× slow-mo means each frame shown 4× in a row — the eye sees a stutter. With it, brand-new in-between frames fill the gap.

Naive (no interpolation): 50 tokens per output-second, 500-token minimum. With interpolation: 200 tokens per output-second, 1,000-token minimum. Cost scales with OUTPUT duration — a 60s clip at 4× slower produces a 240s output and bills on the 240s.

Motion estimation is heavy — ffmpeg has to do a block-matching search between every pair of source frames and synthesize in-between frames pixel-by-pixel. A 4× slow-mo on a 60s clip can take 3-5 minutes of GPU render time vs. 15 seconds for the naive path.

2× slower is the sweet spot for most social clips — noticeable slow-mo without dragging pacing. 4× is dramatic (product reveals, sports replays). 8× super-slow is cinematic but only works well if source is steady high-frame-rate footage.

60fps is the recommended default — smooth on every display. 30fps keeps files small and works for social-standard vertical video. 120fps is cinematic and looks silky on capable displays but doubles the render time. Only matters when FPS interpolation is on.

Two likely reasons: (a) source has heavy motion blur — the interpolator has nothing sharp to track between frames, (b) extreme motion changes direction between frames, defeating block-matching. Try a 2× factor instead of 8×, or shoot at higher frame rate to begin with.

Twixtor is the $330 After Effects plugin pros use for wedding / sports slow-mo. Its motion tracking is measurably smoother than ffmpeg minterpolate on very fast or chaotic motion. For everyday social clips and product shots, minterpolate (AI Slow Motion) matches Twixtor to the eye. For flagship showcase work, Twixtor still wins.

Flowframes is a free Windows GUI over ML-based interpolators (RIFE, FLAVR). Better quality than minterpolate on hard cases, but you need a local GPU with 8+ GB VRAM and about 5 minutes per short clip. AI Slow Motion does it in the cloud — no install, works on every device.

DaVinci Resolve Studio ($295) has Optical Flow (Speed Warp) — excellent quality, but behind a paid Studio license and a full project timeline. For one-off slow-mo you rarely open Resolve for, the browser path here is 10× faster.

No. The source is deleted immediately after rendering. The output MP4 lives on our CDN for 24 hours (7 days for paid users).

Yes. POST multipart to /v1/video/speed/ with `file`, `speed` (0.1-4.0), `interpolate` (true/false), `target_fps` (24-120). Pre-flight quote: GET /v1/video/speed-quote/?duration=SECS&speed=0.25&interpolate=true. Returns output_duration alongside the token estimate. Snippets at /api/.

Sign up free for 10,000 tokens

Create Free Account

No credit card required

How would you rate this tool?

Love Free.ai? Tell your friends!