> ## Documentation Index
> Fetch the complete documentation index at: https://langwatch.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Upload a file

> Upload a file (CSV, JSON, JSONL) to an existing dataset



## OpenAPI

````yaml POST /api/dataset/{slugOrId}/upload
openapi: 3.1.0
info:
  title: LangWatch API
  version: 1.0.0
  description: LangWatch openapi spec
servers:
  - url: https://app.langwatch.ai
security:
  - project_api_key: []
paths:
  /api/dataset/{slugOrId}/upload:
    post:
      description: Upload a file (CSV, JSON, JSONL) to an existing dataset
      operationId: postApiDatasetBySlugOrIdUpload
      parameters:
        - schema:
            type: string
          in: path
          name: slugOrId
          required: true
      responses: {}
components:
  securitySchemes:
    project_api_key:
      type: apiKey
      in: header
      name: X-Auth-Token
      description: >-
        Project API key for sending traces and accessing project-scoped
        resources. Format: sk-lw-... (no underscore). Obtain one by creating a
        project via the Admin API or the LangWatch UI.

````