Public API

Langfuse is open and meant to be extended via custom workflows and integrations. All Langfuse data and features are available via the API.

/api/public

https://us.cloud.langfuse.com/api/public

https://cloud.langfuse.com/api/public

https://hipaa.cloud.langfuse.com/api/public

References:

API Reference: https://api.reference.langfuse.com
OpenAPI spec: https://cloud.langfuse.com/generated/api/openapi.yml
Postman collection: https://cloud.langfuse.com/generated/postman/collection.json

There are 3 different groups of APIs:

This page -> Project-level APIs: CRUD traces/evals/prompts/configuration within a project
Organization-level APIs: provision projects, users (SCIM), and permissions
Instance Management API: administer organizations on self-hosted installations

Authentication

Authenticate with the API using Basic Auth. The API keys are available in the Langfuse project settings.

Username: Langfuse Public Key
Password: Langfuse Secret Key

Example:

curl -u public-key:secret-key https://cloud.langfuse.com/api/public/projects

Access via SDKs

Both the Langfuse Python SDK and the JS/TS SDK provide a strongly-typed wrapper around our public REST API for your convenience. The API methods are accessible via the api property on the Langfuse client instance in both SDKs.

You can use your editor’s Intellisense to explore the API methods and their parameters.

When fetching prompts, please use the get_prompt (Python) / getPrompt (JS/TS) methods on the Langfuse client to benefit from client-side caching, automatic retries, and fallbacks.

When using the Python SDK:

from langfuse import get_client
 
langfuse = get_client()
...
# fetch a trace
langfuse.api.trace.get(trace_id)
 
# async client via asyncio
await langfuse.async_api.trace(trace_id)
 
# explore more endpoints via Intellisense
langfuse.api.*
await langfuse.async_api.*

import { LangfuseClient } from '@langfuse/client';
 
const langfuse = new LangfuseClient();
...
// fetch a trace
await langfuse.api.trace.get(traceId);
 
// explore more endpoints via Intellisense
langfuse.api.*

Install Langfuse by adding the following to your pom.xml:

<dependencies>
  <dependency>
    <groupId>com.langfuse</groupId>
    <artifactId>langfuse-java</artifactId>
    <version>0.0.1-SNAPSHOT</version>
  </dependency>
</dependencies>
 
<repositories>
  <repository>
    <id>github</id>
    <name>GitHub Package Registry</name>
    <url>https://maven.pkg.github.com/langfuse/langfuse-java</url>
  </repository>
</repositories>

Instantiate and use the Java SDK via:

import com.langfuse.client.LangfuseClient;
import com.langfuse.client.resources.prompts.types.PromptMetaListResponse;
import com.langfuse.client.core.LangfuseClientApiException;
 
LangfuseClient client = LangfuseClient.builder()
  .url("https://cloud.langfuse.com") // 🇪🇺 EU data region
  // .url("https://us.cloud.langfuse.com") // 🇺🇸 US data region
  // .url("http://localhost:3000") // 🏠 Local deployment
  .credentials("pk-lf-...", "sk-lf-...")
  .build();
 
try {
  PromptMetaListResponse prompts = client.prompts().list();
} catch (LangfuseClientApiException error) {
  System.out.println(error.getBody());
  System.out.println(error.getStatusCode());
}

Ingest Traces via the API

The OpenTelemetry Endpoint will replace the Ingestion API in the future. Therefore, it is strongly recommended to switch to the OpenTelemetry Endpoint for trace ingestion. Please refer to the OpenTelemetry docs for more information.

OpenTelemetry Traces Ingestion Endpoint implements the OTLP/HTTP specification for trace ingestion, providing native OpenTelemetry integration for Langfuse Observability.
(Legacy) Ingestion API allows trace ingestion using an API.

Retrieve Data via the API

Observations API - Retrieve observation data (spans, generations, events) from Langfuse for use in custom workflows, evaluation pipelines, and analytics. The v2 API offers high-performance data retrieval with cursor-based pagination and selective field retrieval.
Metrics API - Retrieve aggregated analytics and metrics from your Langfuse data. Query across different views (observations, scores) with customizable dimensions, metrics, filters, and time granularity for powerful custom reports and dashboards.

Alternatives

You can also export data via:

UI - Manual batch-exports from the Langfuse UI
Blob Storage - Scheduled automated exports to cloud storage

FAQ

GitHub Discussions

Observations API Query via SDKs

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