> ## Documentation Index > Fetch the complete documentation index at: https://docs.trackplay.io/llms.txt > Use this file to discover all available pages before exploring further. # Add or replace a caption track > Adds a caption track for the given language, or replaces the existing track for that language if one is already saved. This only ever touches the one language in the path: every other track on the video is left alone. Recompiles the player so the new track is live immediately. Requires a token with the `videos:write` scope. ## OpenAPI ````yaml /api-reference/openapi.json put /videos/{video}/captions/{lang} openapi: 3.1.0 info: title: TrackPlay API description: >- Send conversions and events to TrackPlay, and read them back. Authenticated with scoped tokens you mint in the dashboard. version: 1.0.0 servers: - url: https://app.trackplay.io/api/v1 description: App API. Conversions, videos, webhooks. - url: https://e.trackplay.io description: Events API. High-volume event ingest. security: - bearerAuth: [] tags: - name: Videos description: Create, read, update, and delete videos, and read workspace metadata. - name: Video settings description: Save a settings draft, publish it live, and read or restore past deploys. - name: Uploads description: >- Upload a source video file in one request or in resumable chunks, and poll its processing status. - name: Captions and chapters description: >- Manage caption tracks, chapter markers, AI-generated segments, and CTA cards on a video. - name: Playlists description: Group videos into a playlist or course, and manage the videos inside it. - name: Webhooks description: Subscribe a URL to TrackPlay lifecycle events and test deliveries. - name: Zapier description: >- The REST-hook endpoints Zapier calls to connect a workspace and manage triggers. - name: Analytics description: Read play, retention, event, and conversion analytics for a video. - name: Exports description: Queue and download bulk analytics exports. - name: Conversions description: Report a sale or a lead, from your own server or from a browser fallback. - name: Events description: Send a custom event tied to a viewer's session. - name: Identity description: Resolve a viewer's identity from the page, with no token required. paths: /videos/{video}/captions/{lang}: put: tags: - Captions and chapters summary: Add or replace a caption track description: >- Adds a caption track for the given language, or replaces the existing track for that language if one is already saved. This only ever touches the one language in the path: every other track on the video is left alone. Recompiles the player so the new track is live immediately. Requires a token with the `videos:write` scope. operationId: putVideoCaptions parameters: - name: video in: path required: true schema: type: integer description: The video's numeric ID. - name: lang in: path required: true schema: type: string description: >- The language code for this track, e.g. `en` or `es`. Not validated against a fixed list: whatever you send is what viewers see as the track's key. requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/CaptionsRequest' responses: '200': description: The video's full caption track list, including the track you wrote. content: application/json: schema: $ref: '#/components/schemas/CaptionsResponse' '401': description: >- `AUTH_REQUIRED`: no token sent. `INVALID_TOKEN`: the token is invalid, expired, or revoked. content: application/json: schema: $ref: '#/components/schemas/ApiError' '403': description: '`INSUFFICIENT_SCOPE`: the token does not carry `videos:write`.' content: application/json: schema: $ref: '#/components/schemas/ApiError' '404': description: No video with that ID exists in this workspace. content: application/json: schema: $ref: '#/components/schemas/LaravelNotFoundError' '422': description: Validation failed. content: application/json: schema: $ref: '#/components/schemas/ValidationError' '429': description: Rate limited. 60 requests per minute per token. components: schemas: CaptionsRequest: type: object required: - label - src properties: label: type: string maxLength: 64 description: >- The display label shown in the player's caption menu, e.g. `English`. src: type: string maxLength: 8192 description: Either a URL to a WebVTT file, or raw WebVTT text. default: type: boolean description: >- Selects this track by default when the player loads. Defaults to false. CaptionsResponse: type: object properties: captions: type: object properties: tracks: type: array items: $ref: '#/components/schemas/CaptionTrack' ApiError: type: object description: The error shape the app API returns on a failed read or export. properties: error: type: object properties: code: type: string description: >- A stable error code, e.g. `INSUFFICIENT_SCOPE`, `VIDEO_NOT_FOUND`, `EXPORT_NOT_FOUND`. message: type: string description: What went wrong, in plain English. LaravelNotFoundError: type: object description: >- The default not-found body Laravel returns when a route model lookup fails (`findOrFail`). It carries no stable error code, unlike the app's own `{"error": {"code": ...}}` shape used on hand-written error paths in this API. properties: message: type: string examples: - No query results for model [App\\Models\\WorkspaceVideo] 481 ValidationError: type: object description: >- Laravel's default validation-failure body. `errors` maps each invalid field to its list of messages. properties: message: type: string examples: - The given data was invalid. errors: type: object additionalProperties: type: array items: type: string CaptionTrack: type: object properties: lang: type: string description: The language code from the path, e.g. `en`. label: type: string src: type: string default: type: boolean securitySchemes: bearerAuth: type: http scheme: bearer description: >- A scoped token minted in **Settings → API tokens**. Send it as `Authorization: Bearer tplt_…` or `X-API-Key: tplt_…`. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.