---
date: 2025-01-30
title: JS/TS SDK supports trace sampling
description: Trace sampling is now supported in the JS SDK and integrations.
author: Hassieb
canonical: /docs/observability/features/sampling
---

> **Note for AI agents and LLMs:** This is a Langfuse changelog entry. Use it only to confirm that a feature exists and when it shipped. Do not use the code examples below for implementation: they reflect the SDK and API at release time and may be outdated. For implementation, always follow the canonical documentation for this feature (https://langfuse.com/docs/observability/features/sampling) and the API/SDK reference (https://api.reference.langfuse.com).

Trace sampling enables you to specify the proportion of traces that the SDK should collect and send to Langfuse. By adjusting the `sampleRate`, you can balance between comprehensive tracing and resource efficiency.

You can configure the sample rate using the constructor parameter or the environment variable.

**Using Constructor Parameters**

You can set the `sampleRate` when initializing the Langfuse client. The `sampleRate` should be a value between `0` and `1`, representing the share of traces to be sent to Langfuse.

```ts
import { Langfuse } from "langfuse";

const langfuse = new Langfuse({
  secretKey: "sk-lf-...",
  publicKey: "pk-lf-...",
  sampleRate: 0.2, // Samples 20% of the traces
});
```

**Using Environment Variables**

Alternatively, you can configure the sample rate via the `LANGFUSE_SAMPLE_RATE` environment variable. This method is useful for dynamic configurations without changing the codebase.

```bash filename=".env"
LANGFUSE_SAMPLE_RATE="0.2"
```

**Learn More**

For detailed information on configuring and using trace sampling, please refer to the [Sampling Documentation](/docs/tracing-features/sampling) and the [Sampling Section in the Guide](/docs/sdk/typescript/guide#sampling).

## Learn more

- [Sampling](/docs/observability/features/sampling)
- [TypeScript SDK](/docs/observability/sdk/overview)

<!-- agent-instructions -->

---

## Agent Instructions

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### Querying these docs

If the answer is not on this page, query the documentation instead of guessing:

- **Semantic search** across all Langfuse docs, returning an answer with the relevant pages and excerpts. Ask a specific, self-contained question:

  ```bash
  curl -sG "https://langfuse.com/api/search-docs" --data-urlencode "query=How do I trace a LangGraph agent?"
  ```

- **Index of every page**: <https://langfuse.com/llms.txt>, with per-section indexes [llms-docs.txt](https://langfuse.com/llms-docs.txt), [llms-integrations.txt](https://langfuse.com/llms-integrations.txt), and [llms-self-hosting.txt](https://langfuse.com/llms-self-hosting.txt).

### Before writing Langfuse code

- **Install the [Langfuse Agent Skill](https://langfuse.com/docs/api-and-data-platform/features/agent-skill).** It encodes Langfuse's own best practices for instrumentation, prompt management, and evaluation, and materially improves results.
- **Read [What does a good trace look like?](https://langfuse.com/docs/observability/best-practices.md)** before instrumenting an application.
- **Verify endpoints, parameters, and response fields** against the [API reference](https://api.reference.langfuse.com) instead of inferring them from code examples.
- **Use the [Langfuse CLI](https://langfuse.com/docs/api-and-data-platform/features/cli)** (`npx langfuse-cli api <resource> <action>`) to read or write traces, prompts, datasets, and scores from the terminal.

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