Caption Tools Lab v7.1

Shorts Caption Strategy Workbench

Load a local video, tune caption timing on a compact waveform timeline, compare hook angles, map retention beats, check platform safe zones, and run subtitle quality checks, and export SRT/VTT/editor handoff files. No upload is required.

Strategy focus: this is not a full video editor. It is a caption-first shortform lab: compact preview, precise timing, hook battle, retention map, safe-zone risk, and editor handoff.

Why WebM first?

Captioned WebM is rendered locally in your browser, so there is no upload or render server. MP4 remains a future experimental converter because it is heavier in-browser.

Export options

Script & Active Cue

Edit text and timing with the preview nearby and the timeline taking priority.

Local video

Browser-local. MP4/WebM preview depends on codec support.

Safe zone

Caption look

SizeVertical

Script / narration

Target secondsMax chars/cueHighlight words

Active cue timing

StartEnd

Tip: drag the cue body to move it, or drag its left/right edge to resize. Use Set In/Set Out while previewing.

Compact Precision Timeline

Timeline stays compact: click to seek, drag blocks to move, pull edges to trim, and double-click cue text or press the Edit pill to edit inline.

ReadyZoom

Waveform lane ready. Load video to analyze audio where supported.

Caption cues

Drag center = move cue.

Drag edge = trim start/end.

Double-click cue text / Edit pill = edit directly.

Space play/pause · ←/→ seek.

Cue List

Caption Strategy Board

A shortform-first scorecard: hook, readability, density, safe-zone, rhythm, and highlight focus.

Subtitle Quality Checker

SEO-friendly SRT/VTT checks for reading speed, line length, timing overlap, empty cues, first 3 seconds, and shorts readability.

v7.1

This checker gives practical editing warnings, not platform approval. Always preview captions on the target app before final publishing.

Hook Battle

Compare multiple first-caption angles before you commit. Use a version to replace cue 1.

Retention Beat Map

A creator map for the first short: hook, problem, proof, payoff, and loop/CTA.

AI / Strategy Coach

Optional local endpoint. If it fails, the built-in coach still works.

Export Pack

Choose the fastest path for your workflow. Text files are best for editors. Local WebM export gives you a quick captioned video without uploading media to a render server.

Quick finished file

Renders a captioned WebM locally in this browser. Good for previews, drafts, archive files, and YouTube upload testing where WebM is accepted.

No upload

Render rangeQuality

Try to include original audio where the browser supports it

Ready. Load a local video first, then export a short captioned WebM in-browser.

Platform note: WebM is a local, server-free export format. For final TikTok/Reels delivery, MP4 is usually safer; keep SRT/VTT export for CapCut, Premiere, Resolve, or a later optional local MP4 converter.