CaptionLab - Voice-Synced AI Video Captions

Upload Your Video

Drag and drop any MP4, WebM, or MOV video into CaptionLab or select from built-in demo clips. The video is instantly loaded into the preview canvas with zero transcoding delay.

Supported formats: MP4, WebM, QuickTime MOV up to 4K resolution.

Automated AI Voice Transcription

CaptionLab automatically begins transcribing as soon as your video is added. Speech is split into syllables and synchronized with ±10ms acoustic precision.

You can review each word in the live transcript list and click to jump the playback head directly to that word.

Choose Caption Style Template

Switch between preset styles like Viral Karaoke (with active electric yellow glow), Clean Subtitle (monochrome cinema feel), Cyberpunk Neon, or Minimalist Badge.

Customize font size, weight, line-height, text color, and background badge padding to match your brand.

Add Image & Text Elements with Corner Arrow Resize

Brand your video with multiple custom image logos and text watermarks. Drag them directly across the video canvas to position them, and grab any corner arrow handle to interactively resize them in real time.

The bottom-right corner arrow provides 1:1 proportional scaling with live pixel tooltips.

Render Video & Export SRT

Click "Render Video" to burn captions and watermarks directly into a downloadable MP4 right inside your browser, or click "Export SRT" to download industry-standard subtitle timecodes for Premiere Pro or DaVinci Resolve.

Client-side hardware acceleration produces crisp 1080p MP4 exports in seconds with zero cloud waiting queues.

Ready to create your first video?

No credit card or complicated setup required. Jump straight into the CaptionLab studio and see word-by-word sync in action.