> ## 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. # Send an upload chunk > Sends one chunk of raw bytes for a resumable upload session. Send the `Upload-Offset` header set to the number of bytes already sent (0 for the first chunk), and the chunk itself as the raw request body with `Content-Type: application/offset+octet-stream`. This call is idempotent at the current offset: resending the offset you already sent returns the session's current offset unchanged, without writing the chunk twice. Sending an offset ahead of what the session has recorded means a chunk was lost in transit; the call fails with a 409 so you can resend from the session's real offset instead of leaving a gap in the assembled file. Requires a token with the `videos:write` scope. ## OpenAPI ````yaml /api-reference/openapi.json patch /uploads/{upload} 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: /uploads/{upload}: patch: tags: - Uploads summary: Send an upload chunk description: >- Sends one chunk of raw bytes for a resumable upload session. Send the `Upload-Offset` header set to the number of bytes already sent (0 for the first chunk), and the chunk itself as the raw request body with `Content-Type: application/offset+octet-stream`. This call is idempotent at the current offset: resending the offset you already sent returns the session's current offset unchanged, without writing the chunk twice. Sending an offset ahead of what the session has recorded means a chunk was lost in transit; the call fails with a 409 so you can resend from the session's real offset instead of leaving a gap in the assembled file. Requires a token with the `videos:write` scope. operationId: uploadVideoChunk parameters: - name: upload in: path required: true schema: type: string description: The `upload_id` from `POST /videos/{video}/upload/init`. - name: Upload-Offset in: header required: true schema: type: integer description: The number of bytes already sent for this upload, before this chunk. requestBody: required: true content: application/offset+octet-stream: schema: type: string format: binary responses: '200': description: >- The chunk was written, or this offset was already written and the chunk was not repeated. content: application/json: schema: $ref: '#/components/schemas/UploadChunkResponse' '400': description: >- `OFFSET_REQUIRED`: no `Upload-Offset` header. `EMPTY_CHUNK`: zero bytes. `SIZE_EXCEEDED`: the chunk goes past the size declared at init. The body carries the server's real `offset`. content: application/json: schema: $ref: '#/components/schemas/ApiError' '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: '`UPLOAD_NOT_FOUND`: no upload session with that ID, or it expired.' content: application/json: schema: $ref: '#/components/schemas/ApiError' '409': description: >- `OFFSET_MISMATCH`: your `Upload-Offset` is ahead of the server's, so a chunk was lost. Resend from the `offset` in the body. content: application/json: schema: $ref: '#/components/schemas/ApiError' '429': description: Rate limited. 60 requests per minute per token. components: schemas: UploadChunkResponse: type: object properties: offset: type: integer description: >- The total bytes received so far. Send your next chunk's `Upload-Offset` header as this value. size: type: integer description: The size declared at init. 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. 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.