Animated Captions API
The word-by-word caption look, rendered at scale
The bouncing, popping, karaoke-style captions that hold attention on TikTok, Reels, and Shorts — often searched as dynamic captions or dynamic subtitles, generated programmatically. Send a clip and a style, and ZapCap renders the animation into the frames. No frame-by-frame keyframing, no After Effects — and when you want to fine-tune by hand, the same styles are in the ZapCap web editor.
How creators get this look — and why an API beats it at scale
The animated caption style is hand-built in editing apps one clip at a time. To produce it across hundreds of videos, you need it as a render parameter, not a manual edit.
OPTION 01
- Great for a single clip
- Hand-edit every video
- No programmatic access
- Doesn't scale to a pipeline
OPTION 02
- Total creative control
- Slow, expensive per clip
- No API to drive it
- Hard to standardize a look
OPTION 03 · YOU ARE HERE
- Word-pop, karaoke, scale bumps
- Toggle animation per task
- Rendered into the frames
- Same look across every clip
OPTION 04
- Timed text only
- No animation
- No styling
- Off by default on social
How the Animated Captions API works
Upload a clip, create a task with animation enabled and a templateId, then poll or get a webhook. ZapCap renders the word-by-word animation into the frames and hands you a finished MP4.
- 1
Upload your video
POST the file to /videos. We stream it to storage and hand you back a videoId.
POSTPOST /videos - 2
Create the captioning task
One POST starts transcription, styling and rendering with your chosen template. Add a notification webhook to skip polling.
POSTPOST /videos/:id/task - 3
Receive the webhook
We POST status updates to your endpoint as the render moves through transcribing → rendering → completed.
HOOKPOST → your URL - 4
Download the finished render
Burned-in subtitles, served from a global CDN. No watermark. MP4 ready for any social platform.
GETGET renderUrl
POST /videos·Upload your video
Same hook, four animated styles
Each clip is the same source with animation on and a different templateId. The motion is rendered into the pixels — it plays the same in every feed, with no client-side animation engine.
Source is a 9:16 vertical clip. Animated captions are baked into the frames, so the pop, fill, and emphasis survive download and re-upload to any platform.
Pick the motion
Tune the emphasis.
Send a templateId for a complete animated look, or control the motion directly. Animation, word-by-word reveal count, keyword emphasis, font, and position all toggle independently on the task body.
- Animated templates — Beast, Hormozi, Tracy, Devin, plus 25 more (29 presets) — each captures a complete animated caption look.
- Animation — word-by-word pops, karaoke fill, fade in/out, scale bumps — switched on per task.
- displayWords — control how many words appear per cue so the reveal pacing fits the edit.
- Keyword emphasis — flag punchwords; ZapCap colors / scales / boxes them so the hook lands.
- Layout — font, color, stroke, shadow, vertical position with safe-zone math.
{
"templateId": "46d20d67-255c-4c6a-b971-31fddcfea7f0",
"renderOptions": {
"subsOptions": {
"emphasizeKeywords": true,
"animation": true,
"displayWords": 2
},
"styleOptions": {
"fontUppercase": true,
"fontShadow": "l"
}
}
}Animated Captions API transcript options
Auto-transcribe
ZapCap transcribes and times the words so the animation lands on the right beat. Edit any cue, then render the animated captions against the approved transcript.
- Inspect the transcript on the task status, edit via PUT /videos/:id/task/:taskId/transcript
- Word-level timing drives the per-word animation
- Re-render the same transcript into multiple animated styles
Bring your own transcript
Have approved cues already? Send them and ZapCap animates them without retranscribing — handy for scripted hooks and repurposed long-form clips.
- Supported via the SRT-to-burned-in workflow
- Preserve approved wording and punchlines
- Animate the same script into N variants for A/B testing
Animated Captions API output modes
Burned-in MP4
The animated captions are rendered into the source frames — the pop and fill play identically on TikTok, Reels, and Shorts, with sound off.
Transparent overlay
The animated caption layer with alpha preserved, so you can drop the motion over your own cut in an NLE — no chroma key.
Green-screen layer
For tools without alpha support. Animated captions on a #04F404 canvas you key out in your editor or live tool.
Burned-in animated captions are the standard for short-form social. Choose an alpha overlay only if you composite the animated captions over your own edit downstream.
Animate captions in any language
Set a target language and ZapCap transcribes, translates, and animates captions in that language. CJK and Thai use language-aware line-breaking so per-word animation lands on real word boundaries, not whitespace.
- Repurpose one clip into animated captions for multiple markets
- A brand-term dictionary keeps product names accurate in the animated text
- Language-aware word splitting for Chinese, Japanese, Thai
Per-minute, usage-based credits
Pay for the minutes you render. Animation is part of the render — no separate motion-graphics fee. See pricing for the full multiplier table.
- Top up credits to keep clips flowing in production
- Volume credits available at scale
- No per-seat fee — pay for renders, not users
Indicative starting rate. Final pricing depends on render mode and output format. API access requires a Pro plan plus credits.
A short-form content studio produced animated captions across hundreds of clips a week by making the look a render parameter instead of a manual edit
Editors stopped hand-animating captions per video. One templateId and an animation flag now produce a consistent, on-brand animated look on every clip, rendered into the frames and ready to post.
About the Animated Captions API
Animated captions reveal and emphasize words with motion — word-by-word pops, karaoke-style fills, fades, and scale bumps — instead of showing a static block of text. Teams also call them dynamic captions or dynamic subtitles. ZapCap renders this animation into the video frames programmatically for TikTok, Reels, and Shorts. Motion is a template parameter on ZapCap’s video captioning API, not a manual edit.
Set animation to true under subsOptions on the render task, and pick a templateId for the overall look. You can also tune displayWords to control how many words appear per cue, which sets the pacing of the per-word reveal.
No. The animation is rendered directly into the video frames, so it plays identically in every feed and player, with sound off, and survives download and re-upload. There is no client-side animation engine to ship.
Yes — that is the point of the API. Reuse one templateId with the same renderOptions across every task and the animated caption look stays consistent across all your clips and editors, without hand-editing each video.
Yes. Bring your own cues and ZapCap animates them without retranscribing. Word-level timing from the transcript drives the per-word animation, so scripted hooks and repurposed long-form clips animate correctly.
Yes. The same task can return the animated caption layer as a transparent overlay (ProRes 4444 or VP9 with alpha) or a green-screen layer, so you can composite the motion over your own edit.
Related caption rendering APIs
Subtitle API
The umbrella styled subtitle rendering API: video in, captioned video out.
Transparent Subtitle Overlays API
Alpha-channel animated caption layers for editing pipelines.
Green-Screen Subtitles API
The same animated styles on a keyable green canvas for tools that cannot read alpha.
SRT to Burned-In Subtitles API
Render an existing, approved SRT into a styled MP4 — no retranscription.
Webhook Video Captioning API
Async caption workflows with signed events, retries, and eventId-based dedupe.
Render animated captions through the API
Create a key on a Pro plan and buy credits in the dashboard.