Shorts Lab
Drop a long video → AI detects the best 30-second hook → crop to 9:16 vertical → burn TikTok-style subtitles → download MP4. Everything runs in your browser. Free alternative to OpusClip and Munch.
Drop your video here
MP4, MOV, WebM — any format your browser can play
Best results: 2–20 minutes of talking-head or interview content
Whisper AI Transcription
Transcription lets the tool detect the best hook and generate subtitles. Skip if you don't need subtitles.
Select the spoken language for accurate subtitles.
First-time download only · cached in browser afterwards
Transcript
↕ Drag on preview to reposition crop
✨ AI-Suggested Hooks
Click to jump to the best 30s windows detected by AI.
Hooks appear after transcription.
🎬 Frame & Crop
Or drag the preview above to fine-tune manually.
💬 Subtitle Style
📝 Edit Subtitles
Click any segment to fix transcription errors.
Transcript appears here after transcription.
Export your Short
The free alternative to OpusClip and Munch
Tools like OpusClip and Munch charge $20–150/month to take a long video, find the best moments, reframe to 9:16 and add subtitles. They process everything on their servers with a monthly clip quota. Shorts Lab does the same workflow entirely in your browser, with no monthly limit and no server costs — because your CPU does all the work.
The 4-step workflow
- Upload — drop any video file. MP4, MOV, WebM — anything your browser can play.
- Transcribe — Whisper AI (same model used by OpenAI's API) transcribes the audio with word-level timestamps. Or skip this step if you just want the crop.
- Edit — the AI suggests the 3 most "hook-worthy" 30-second windows based on speech density. Pick one, or drag the timeline handles to any custom range. Preview with live subtitle rendering.
- Export — WebCodecs encodes a full-quality MP4 with subtitles burned in, ready to upload to TikTok, Instagram Reels or YouTube Shorts.
Hook detection
We use a sliding-window algorithm that scores each 30-second segment by the number of words spoken per second. High speech density correlates with high-energy moments — the parts where the speaker is most engaged, making their point, or delivering value. The top 3 windows are ranked and shown as clickable suggestions.
Subtitles
Subtitles are rendered directly onto the video frames during export using the Canvas API. Three styles are available: TikTok (bold text on a semi-transparent box, yellow accent — the most viral-looking style), Minimal (white text with a drop shadow, clean and readable), and Solid Box (colorful background, high contrast).
Privacy
Your video never leaves your device. All transcription, cropping and encoding happen locally using WebAssembly and WebCodecs. The only network requests are the one-time model downloads (Whisper model from HuggingFace, both cached by your browser after the first run).
Limitations
- Export requires WebCodecs — Chrome/Edge 94+ or Safari 16.4+.
- Transcription requires a model download (75–145 MB) on first use.
- Encoding speed depends on your CPU — expect 1–3 minutes per 30-second clip.
- Very long videos (>60 min) may run out of browser memory during audio decoding.
Frequently Asked Questions
- What is Shorts Lab?
- A tool to convert landscape videos into vertical 9:16 format for YouTube Shorts, TikTok, and Instagram Reels.
- Does it add watermarks to my videos?
- No, the output is clean with no watermarks or branding.
- Can I preview the crop before exporting?
- Yes, see a live preview of how your video will look in vertical format.
- Does it process videos on a server?
- No, everything runs locally in your browser for maximum privacy.
- Is Shorts Lab free to use?
- Yes, unlimited conversions with no cost or sign-up.