Bringing
captions to life

Start for free See how it works

Powering the next generation of video creators, studios, and developers. From karaoke-style word highlighting to brand watermarks, automated transcription, and one-click SRT export.

Live transcription
● 70+ languages supported
CaptionLab AI Video Caption Editor Interface
Live Word Sync • Sub-10ms Accuracy
AI Acoustic Sync Alignment
Video Caption Styles: Viral Karaoke, Clean Subtitle, Cyberpunk Neon, Pastel Social
POST https://api.captionlab.io/v1/transcribe
Request Code • Sub-10ms Alignment
1import { CaptionLab } from '@captionlab/sdk';
2
3const client = new CaptionLab({ apiKey: process.env.CAPTION_API_KEY });
4const result = await client.transcribe({
5  videoUrl: 'https://media.acme.com/podcast.mp4',
6  highlightMode: 'karaoke-glow', activeColor: '#FFD000'
7});
8const srt = result.toSRT(); // Sub-10ms synchronized timecodes
1from captionlab import CaptionClient
2
3client = CaptionClient(api_key=os.getenv("CAPTION_API_KEY"))
4response = client.transcribe(
5    video_url="https://media.acme.com/podcast.mp4",
6    style_preset="viral-karaoke", highlight_color="#FFD000"
7)
8print(f"Synced {len(response.words)} words with sub-10ms precision")
1curl -X POST https://api.captionlab.io/v1/transcribe \
2  -H "Authorization: Bearer $CAPTION_API_KEY" \
3  -H "Content-Type: application/json" \
4  -d '{
5    "videoUrl": "https://media.acme.com/podcast.mp4",
6    "highlightMode": "karaoke-glow", "activeColor": "#FFD000"
7  }'
Synchronized JSON Response 200 OK • 142ms 
{
  "status": "completed", "duration_sec": 42.85, "accuracy": 0.994,
  "captions": [{
    "start": 0.32, "end": 2.15, "text": "Level up your video content",
    "words": [
      { "w": "Level", "s": 0.32, "e": 0.65, "color": "#FFD000" },
      { "w": "up", "s": 0.65, "e": 0.88, "color": "#FFD000" },
      { "w": "your", "s": 0.88, "e": 1.12, "color": "#FFD000" },
      { "w": "content", "s": 1.12, "e": 2.15, "color": "#FFD000" }
    ]
  }],
  "srt_export": "https://api.captionlab.io/v1/sub_92f8.srt"
}
• SRT Subtitles • WebVTT • ASS Karaoke • 10,000 req/min
Explore Developer API Documentation →
Karaoke Highlight Live Transcription Brand Watermarks Style Templates SRT Subtitles
Open Studio →
Powering creators, studios & developers worldwide
ContentForge
StreamHub
PodcastPro
GlobalDub
SocialClip
EduStream
CorpMedia
FilmStudio
BroadcastAI
ContentForge
StreamHub
PodcastPro
GlobalDub
SocialClip
EduStream
CorpMedia
FilmStudio
BroadcastAI
Core Platform

Everything captions
need to be perfect

Word Highlighting

Karaoke-style,
word-by-word

Every word illuminates exactly as it's spoken. Choose from four highlight modes - glowing yellow, background badge, scale pulse, or combined - to make every video pop on social feeds.

Karaoke Glow Electric Yellow Sub-10ms Sync
Karaoke Video Caption Word Highlighting Sync
Templates & Presets

Proven templates.
Infinite custom styles.

From Bold Viral Social to Clean Netflix Subtitles, Cyberpunk Neon, and Minimal Clean. Fully customizable font sizes, weights, background pads, and dynamic borders.

Open style editor →
Video Caption Styles: Viral Karaoke, Clean Subtitle, Cyberpunk Neon, Pastel Social
Brand Protection

Watermarks with
pixel-perfect control

Upload PNG, SVG, or text watermarks. Position them anywhere on the video canvas with 9 anchor presets, control opacity from 10% to 100%, and brand your content automatically.

PNG & SVG Logos Opacity 10-100% 9 Anchor Grid
Watermark Placement and Brand Protection Editor
Real-Time Acoustic Synchronization
Our audio engine aligns speech syllables with video frames at sub-10ms precision. No drifting captions, no awkward cuts - text illuminates precisely when voiced.
Try live demo →
70+ Languages
Transcribe English, Spanish, Hindi, Japanese, French, Arabic, and dozens more with specialized industry vocabularies.
View languages →
One-Click SRT Export
Export timecode-accurate SRT files compatible with Premiere Pro, Final Cut, DaVinci Resolve, YouTube, and TikTok.
Export details →
Full Visual Customization
Font family, size, line-height, text color, highlight color, background badge, border stroke, and shadow - tuned in real time.
See styles →
Zero Cloud Leaks
Self-hostable via Docker Compose. Your video never leaves your private cloud or local machine unless you explicitly choose to upload it.
Self-hosting docs →
Engineered for creators who care about every single millisecond
±10ms
Word-level timestamp accuracy powered by AI Acoustic Alignment
70+
Languages transcribed with dialect and accent adaptation
6x
Faster caption turnaround compared to manual subtitle editors
100%
Open source and self-hostable with full privacy guarantees
Creator Stories

What creators are saying

View all stories →
“CaptionLab turned our daily video podcast into viral, highly shareable social clips. The karaoke highlighting sync is so tight it looks like it was hand-animated frame by frame.”
Marcus Sterling
Head of Production, StreamForge Media
“We cut our subtitle editing workflow from 45 minutes down to 3 minutes per video. The SRT export drops straight into Premiere without any timing drift.”
Elena Rostova
Video Director, SocialPulse Agency
“Our students need clear, accessible captions across multiple accents. The AI speech engine handles technical terminology flawlessly.”
Dr. Aris Thorne
Director of E-Learning, GlobalAcademy
Privacy & Security

Built with privacy at the core

Your raw media never leaves your browser unless you choose to store it. CaptionLab is designed with zero tracking, local indexed storage, and transparent data practices.

Local Media Processing
Videos are decoded and previewed directly in your browser. No third-party ad tracking, no video harvesting.
Direct API Key Use
Your private API key stays in your session. Audio processing connects securely without intermediate data logging.
Open Source & Auditable
CaptionLab is MIT-licensed. Audit every line of code, fork the repo, or run your own private instance in Docker.
Flexible Plans

Simple, Transparent Pricing

Start with 150 minutes free every month. Upgrade as your channel or studio expands.

MonthlyAnnual(Save 20%)
FREE STARTER
Starting at
$0| Month

For individuals looking to create voice-synced viral captions.

Get Started Free
QUOTA & LIMITS
  • 150 minutes included
  • 10 min max video length
  • Local browser storage
STUDIO FEATURES
  • Sub-10ms acoustic word sync
  • Karaoke word highlights
  • 4 Built-in viral presets
  • PNG & SVG Brand watermarks
  • 1-Click SRT subtitle export
CREATOR PROPopular
Starting at
$15| Month

For individuals looking to grow their channels and social media presence.

Upgrade to Creator Pro
QUOTA & LIMITS
  • 600 minutes included
  • 60 min max video length
  • Priority GPU transcription queue
PRO SUITE
  • Everything in Free Starter
  • 4K Ultra-HD video rendering
  • Custom font uploads (.otf, .ttf)
  • Auto-rechunking pause rules
  • Commercial broadcast & ad rights
  • Priority email & chat support
ENTERPRISE
Starting at
Custom| Month

For production houses and studios looking to scale video operations.

Contact Sales Team
TEAM & SCALE
  • Unlimited minutes included
  • Unlimited length per video
  • Self-hosted Docker Compose / VPC
ENTERPRISE SUITE
  • REST API & Webhooks
  • Multi-seat workspace & collaboration
  • Custom acoustic vocabulary models
  • 99.9% Uptime SLA & dedicated Slack
  • Dedicated Account Manager
View Full Feature Breakdown & Comparison

Compare all 18+ studio features, FAQs, and custom limits on our Pricing Page.

AI Video Captioning Platform
See demo Start captioning free