TypeScript SDK - Setup

Installation

Install the relevant packages for a full tracing setup:

npm install @langfuse/tracing @langfuse/otel @opentelemetry/sdk-node

• @langfuse/tracing: Core tracing functions (startObservation, startActiveObservation, etc.)
• @langfuse/otel: The LangfuseSpanProcessor to export traces to Langfuse.
• @opentelemetry/sdk-node: The OpenTelemetry SDK for Node.js.

Learn more about the packages here.

Register your credentials

Add your Langfuse credentials to your environment variables. Make sure that you have a .env file in your project root and a package like dotenv to load the variables.

LANGFUSE_SECRET_KEY = "sk-lf-..."
LANGFUSE_PUBLIC_KEY = "pk-lf-..."
LANGFUSE_BASE_URL = "https://cloud.langfuse.com" # 🇪🇺 EU region
# LANGFUSE_BASE_URL = "https://us.cloud.langfuse.com" # 🇺🇸 US region

Initialize OpenTelemetry

The Langfuse TypeScript SDK’s tracing is built on top of OpenTelemetry, so you need to set up the OpenTelemetry SDK. The LangfuseSpanProcessor is the key component that sends traces to Langfuse.

import { NodeSDK } from "@opentelemetry/sdk-node";
import { LangfuseSpanProcessor } from "@langfuse/otel";
 
const sdk = new NodeSDK({
  spanProcessors: [new LangfuseSpanProcessor()],
});
 
sdk.start();

The LangfuseSpanProcessor is the key component that sends traces to Langfuse.

For more options to configure the LangfuseSpanProcessor such as masking, filtering, and more, see the advanced usage.

You can learn more about setting up OpenTelemetry in your JS environment here.

Installation

npm install @langfuse/client

Register your credentials

Add your Langfuse credentials to your environment variables. Make sure that you have a .env file in your project root and a package like dotenv to load the variables.

LANGFUSE_SECRET_KEY = "sk-lf-..."
LANGFUSE_PUBLIC_KEY = "pk-lf-..."
LANGFUSE_BASE_URL = "https://cloud.langfuse.com" # 🇪🇺 EU region
# LANGFUSE_BASE_URL = "https://us.cloud.langfuse.com" # 🇺🇸 US region

Initialize the client

Initialize the LangfuseClient to interact with Langfuse. The client will automatically use the environment variables you set above.

import { LangfuseClient } from "@langfuse/client";
 
const langfuse = new LangfuseClient();

import { LangfuseClient } from "@langfuse/client";
 
const langfuse = new LangfuseClient({
  publicKey: "your-public-key",
  secretKey: "your-secret-key",
  baseUrl: "https://cloud.langfuse.com", // or your self-hosted instance
});