> ## Documentation Index > Fetch the complete documentation index at: https://docs.dify.ai/llms.txt > Use this file to discover all available pages before exploring further. # Update Child Chunk > Update the content of an existing child chunk. ## OpenAPI ````yaml /en/api-reference/openapi_service.json patch /datasets/{dataset_id}/documents/{document_id}/segments/{segment_id}/child_chunks/{child_chunk_id} openapi: 3.0.1 info: title: Dify Service API description: >- REST API for Dify applications and knowledge bases. Application endpoints authenticate with an app API key; knowledge endpoints authenticate with a dataset API key. version: 1.0.0 servers: - url: https://{api_base_url} description: >- Base URL of the Dify Service API. For self-hosted deployments, replace it with your own API base URL. variables: api_base_url: default: api.dify.ai/v1 description: Host and path of the API base URL, without the `https://` prefix. security: - ApiKeyAuth: [] tags: - name: Chat Messages description: Operations related to chat messages and interactions. - name: Files description: File upload and preview operations. - name: End Users description: Operations related to end user information. - name: Feedback description: User feedback operations. - name: Conversations description: Operations related to managing conversations. - name: Audio description: Text-to-Speech and Speech-to-Text operations. - name: Applications description: Operations to retrieve application settings and information. - name: Annotations description: Operations related to managing annotations for direct replies. - name: Human Input description: Endpoints for resuming paused workflows that require human input. - name: Workflow Runs description: Operations for executing and managing workflows. - name: Completion Messages description: Operations related to text generation and completion. - name: Knowledge Bases description: >- Operations for managing knowledge bases, including creation, configuration, and retrieval. - name: Documents description: >- Operations for creating, updating, and managing documents within a knowledge base. - name: Chunks description: Operations for managing document chunks and child chunks. - name: Metadata description: >- Operations for managing knowledge base metadata fields and document metadata values. - name: Tags description: Operations for managing knowledge base tags and tag bindings. - name: Models description: Operations for retrieving available models. - name: Knowledge Pipeline description: >- Operations for managing and running knowledge pipelines, including datasource plugins and pipeline execution. paths: /datasets/{dataset_id}/documents/{document_id}/segments/{segment_id}/child_chunks/{child_chunk_id}: patch: tags: - Chunks summary: Update Child Chunk description: Update the content of an existing child chunk. operationId: updateChildChunk parameters: - name: dataset_id in: path required: true schema: type: string format: uuid description: Knowledge base ID. - name: document_id in: path required: true schema: type: string format: uuid description: Document ID. - name: segment_id in: path required: true schema: type: string format: uuid description: Chunk ID. - name: child_chunk_id in: path required: true schema: type: string format: uuid description: Child chunk ID. requestBody: required: true content: application/json: schema: type: object required: - content properties: content: type: string description: Child chunk text content. responses: '200': description: Child chunk updated successfully. content: application/json: schema: type: object properties: data: $ref: '#/components/schemas/ChildChunk' examples: success: summary: Response Example value: data: id: d7e8f9a0-1b2c-3d4e-5f6a-7b8c9d0e1f2a segment_id: f3d1c7be-9f3a-40d8-8eb8-3a1ef9c3f2c1 content: Dify is an open-source platform. position: 1 word_count: 6 type: customized created_at: 1741267200 updated_at: 1741267200 '400': description: '`invalid_param` : Failed to update the child chunk index.' content: application/json: examples: invalid_param: summary: invalid_param value: status: 400 code: invalid_param message: Update child chunk index failed. '403': description: >- - `forbidden` : Dataset api access is not enabled. - `forbidden` : The capacity of the vector space has reached the limit of your subscription. - `forbidden` : Sorry, you have reached the knowledge base request rate limit of your subscription. - `forbidden` : To unlock this feature and elevate your Dify experience, please upgrade to a paid plan. content: application/json: examples: forbidden_1: summary: forbidden (api access) value: status: 403 code: forbidden message: Dataset api access is not enabled. forbidden_2: summary: forbidden (vector space) value: status: 403 code: forbidden message: >- The capacity of the vector space has reached the limit of your subscription. forbidden_3: summary: forbidden (rate limit) value: status: 403 code: forbidden message: >- Sorry, you have reached the knowledge base request rate limit of your subscription. forbidden_4: summary: forbidden (upgrade plan) value: status: 403 code: forbidden message: >- To unlock this feature and elevate your Dify experience, please upgrade to a paid plan. '404': description: |- - `not_found` : Dataset not found. - `not_found` : Document not found. - `not_found` : Segment not found. - `not_found` : Child chunk not found. content: application/json: examples: not_found_1: summary: not_found value: status: 404 code: not_found message: Dataset not found. not_found_2: summary: not_found value: status: 404 code: not_found message: Document not found. not_found_3: summary: not_found value: status: 404 code: not_found message: Segment not found. not_found_4: summary: not_found value: status: 404 code: not_found message: Child chunk not found. components: schemas: ChildChunk: type: object properties: id: type: string description: Unique identifier of the child chunk. segment_id: type: string description: ID of the parent chunk this child chunk belongs to. content: type: string description: Text content of the child chunk. position: type: integer description: Position of the child chunk within the parent chunk. word_count: type: integer description: Word count of the child chunk content. type: type: string description: >- How the child chunk was created. Child chunks created or updated through the API are always `customized`. System-generated child chunks are `automatic`. created_at: type: number description: Creation timestamp (Unix epoch in seconds). updated_at: type: number description: Last update timestamp (Unix epoch in seconds). securitySchemes: ApiKeyAuth: type: http scheme: bearer bearerFormat: API_KEY description: >- API Key authentication. For all API requests, include your API Key in the `Authorization` HTTP Header, prefixed with `Bearer `. Example: `Authorization: Bearer {API_KEY}`. **Strongly recommend storing your API Key on the server-side, not shared or stored on the client-side, to avoid possible API-Key leakage that can lead to serious consequences.** Requests with a missing or invalid API key fail with HTTP `401` and error code `unauthorized`. ````