---
title: "Start Preview"
method: POST
path: "/lc.preview.startpreview"
tags: ["Preview Provider"]
---

# Start Preview

`POST /lc.preview.startpreview`

This endpoint initiates the preview generation. It initiates an asynchronous background job to generate the preview. The timeout for this request which initiates the background job should be 10 seconds. The Response will be sent on the callbackUrl and not from this request.
 [Callback Response](#/schemas/PreviewProvider.MainResponse)

## Headers

- `X-LC-ExtensionPointVersion` string
- `X-LC-ExtensionId` string
- `X-LC-AppVersion` string
- `TR_ID` string
- `x-lc-signature` string

## Request body

- PreviewProviderMainRequest — Request for StartPreview or RefreshPreview
  - `previewSessionId` string, required — Unique identifier for the given Preview Session.
  - `scope` 'source' | 'target' — It indicates whether the source or the target is being generated.
  - `fileInformation` PreviewProviderFileInformation
    - `name` string — The name of the file.
    - `sourceLanguage` string — The source language of the file.
    - `targetLanguage` string — The target language of the file.
  - `inputFiles` object, required
    - `nativeFileUrl` string — It defines the one time download URL for the input native source file or for the native target file, depending on the generation scope.
    - `bilingualDocumentUrl` string — It defines the onetime download URL for the input BCM document.
    - `previewPackageTemplateUrl` string — It defines the onetime download URL for the input previewPackageTemplate.
    - `nativeAnnotatedFileUrl` string — It defines the one time download URL for the input native annotated sourceFile or for the native annotated target file, depending on the generation scope.
  - `previewResultFileUrl` string — Defines the one time upload URL to upload either a generated previewPackage or a previewHtmlFile.
  - `callbackUrl` string, required — This is the URL detailing endpoint to call when the asynchronous job has completed.

## Response `202`

Accepted

## Other responses

- `400` — Bad Request
- `401` — Unauthorized

## Changes

- **2026-01-27** (v1) `9d9d8922a0ce` — 3 info
  - the endpoint scheme security `LanguageCloudJWSToken` was removed from the API
  - added the new optional `header` request parameter `TR_ID`
  - added the new optional `header` request parameter `x-lc-signature`

[Change history](https://skmtc.dev/rws/apis/app-api/changes/lc.preview.startpreview/post.md)

---

[API](https://skmtc.dev/rws/apis/app-api.md) · [All operations](https://skmtc.dev/rws/apis/app-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/rws/app-api/revisions/a06e1ee1c99b/schema)