The captioning API for styled, burned-in subtitles

ZapCap renders captions through one API

Send a video, choose a style, get a finished captioned MP4, a transparent overlay, or a green-screen layer back. Not a transcript API — finished captioned video, programmatically. (Prefer a UI? The same engine powers the web editor at zapcap.ai.) Webhook-native. Multilingual. Per-minute pricing.

Create API key Read API docs OpenAPI spec

API access on the Pro plan · buy render credits in the dashboard

Capabilities Quickstart Outputs Use cases Languages Compare Case studies Explore Resources Pricing

Why this API exists

Captions are the last mile — ZapCap renders them

Transcription APIs return text. Video automation APIs need you to design a template. ZapCap fills the gap in between — finished, styled captioned video, returned by a single task call.

Not a transcript API — we ship the rendered video, with captions baked in.
No template to design — no scenes, no timelines, no templates to maintain — one task call.
Backend-first — a clean REST API for SaaS, agencies, and ad ops — with the zapcap.ai web editor when you want a UI.

Capabilities

Six product surfaces, one task model

Pick the one closest to your job.

Subtitle API

Video in, styled captioned MP4 out. The main commercial endpoint.

Animated captions

TikTok / Reels / Shorts caption styles, rendered into video.

SRT → burned-in

Approved transcript in, styled MP4 out. No retranscription.

Webhook captioning

Async caption workflows with signed events and retries.

Transparent overlays

Alpha-channel caption layers for NLE timelines.

Green-screen subtitles

Caption layer with chroma backdrop for live + legacy tools.

Quickstart

Three endpoints, the whole API

Upload a video, create a render task, receive a webhook. Everything else — caption layout, transcription, translation, animation — happens server-side.

POST/videos

Upload

Send a remote URL or multipart upload. Returns a videoId.

POST/videos/:id/task

Create render task

Pick a templateId, set render options, attach a webhook notification.

GET/videos/:id/task/:taskId

Poll task (optional)

Webhook-first, but polling works if your stack doesn't accept callbacks.

1# Upload a video URL

2curl https://api.zapcap.ai/videos/url \

3 -H "x-api-key: $ZAPCAP_KEY" \

4 -d '{"url":"https://cdn.acme.com/clip.mp4"}'

6# Create a task with a caption template

7# fetch IDs from GET /templates

8curl https://api.zapcap.ai/videos/$ID/task \

9 -H "x-api-key: $ZAPCAP_KEY" \

10 -d '{

11 "templateId": "<TEMPLATE_UUID>",

12 "language": "en",

13 "notification": {

14 "type": "webhook",

15 "notificationsFor": ["render"],

16 "recipient": "https://acme.com/hooks/zapcap"

17 }

18 }'

20# Webhook fires →

21# { taskId, event: "completed", notificationFor: "render", renderUrl }

Output modes

Pick the format your pipeline wants

Burned-in MP4

Captions baked into the source frames. The right answer for TikTok, Reels, Shorts, ad creative.

Transparent overlay

Alpha-channel caption layer — MOV ProRes 4444 or WebM VP9 alpha — for NLE compositing.

Green-screen layer

Caption layer with #04F404 backdrop, for editors and live tools without alpha support.

Built for production caption workflows

Who ships with the ZapCap API

AI video SaaS captioning API

Outsource caption rendering instead of building ASR + queue + ffmpeg.

Performance creative localization API

Turn winning ad concepts into localized caption variants — fast enough to test.

E-commerce video localization API

One product video, multiple markets, consistent caption styling.

TikTok Shop video localization API

9:16 safe-zone aware caption variants for cross-border social commerce.

Agency video captioning API

Reusable client-style presets, webhook delivery into your client portal.

Multilingual subtitle rendering API

Translate, restyle, and re-render in CJK, Thai, and beyond.

Script-aware caption rendering

Languages most renderers get wrong

Correct segmentation, line-breaking, and glyph shaping for scripts that break naive caption renderers — CJK, Thai, and the wider Southeast Asian set.

Chinese Subtitles API

Han segmentation and line-breaking that does not split mid-character.

Japanese Subtitles API

Kinsoku-aware line breaking and correct kana/kanji shaping.

Thai Subtitles API

Dictionary word-breaking for a script with no spaces, intact combining marks.

CJK Subtitle Rendering API

One endpoint for Chinese, Japanese, and Korean caption rendering.

Southeast Asian Captioning API

Thai, Vietnamese, and neighbours with correct diacritics and shaping.

Compare captioning APIs

Choose ZapCap when captioning is the job

General video-automation APIs render scenes from templates you design. Transcription APIs return text. ZapCap is the captioning API for existing videos: one task call returns the styled captioned file.

Submagic API alternative

Caption-API workflow, pricing, transcript reuse.

VEED API alternative

Workflow control vs marketplace billing.

Creatomate API alternative

Captioning specialist vs general video automation.

Shotstack API alternative

Caption task model vs full JSON timeline.

Bannerbear API alternative

Caption rendering vs image / template automation.

JSON2Video API alternative

Existing-video captioning vs JSON scene generation.

fal auto-caption API alternative

Dedicated caption rendering vs a general model-inference platform.

How teams ship with ZapCap

Caption pipelines, in production

Anonymized accounts of teams that replaced in-house captioning stacks with the ZapCap API.

AI video SaaS captioning case study

Seed-stage product shipped captions in one sprint instead of building a rendering stack.

Agency caption workflow case study

One caption pipeline across every client, delivered by webhook.

E-commerce video localization case study

One master video, many markets, consistent caption styling.

Performance creative localization case study

In-house ad team turned winning concepts into localized variants on tap.

More ways in

Three ways into the captioning API

Past the reference and quickstart above, three guides come at the API from a different angle — a competitor comparison, a worked integration guide, or a production case study.

Pricing

Per-minute API credits, usage-based

Pay $0.10/min for rendered video. Volume credits and dedicated capacity are available when you outgrow the dashboard plan.

View pricing Talk to us about volume