# Langfuse review

> Langfuse is an open source LLM engineering platform for tracing, evaluating, prompt management, and debugging LLM applications and agents.

Devtoolwatch Board, the week of Oct 25–31, 2026. Canonical page: https://index.devtoolwatch.com/tools/langfuse/

## TL;DR

Langfuse is an open source platform for tracing, evaluating, and improving LLM applications and AI agents. Langfuse is for teams building LLM apps who want observability, prompt management, evaluations, and datasets in one place. Langfuse can run as a managed cloud service or be self-hosted with Docker Compose, Kubernetes, or Terraform.

## Langfuse at a glance

- **Category:** [Evals and observability](https://index.devtoolwatch.com/categories/evals-and-observability/)
- **Maintained by:** Langfuse (organization, [@langfuse](https://github.com/langfuse) on GitHub)
- **Language:** TypeScript, Rust, JavaScript
- **Repository:** [github.com/langfuse/langfuse](https://github.com/langfuse/langfuse)
- **Website:** [langfuse.com](https://langfuse.com)
- **npm package:** [langfuse](https://www.npmjs.com/package/langfuse) 3.39.2
- **PyPI package:** [langfuse](https://pypi.org/project/langfuse/) 5.0.4
- **Latest release:** [v4.67.0](https://github.com/langfuse/langfuse/releases/tag/v4.67.0) on GitHub, Oct 21, 2026
- **First published:** May 18, 2023

## What Langfuse does

- Langfuse ingests traces of LLM calls, retrieval, embedding, and agent actions so you can inspect and debug logs and user sessions.
- Langfuse manages prompts centrally with version control, using server- and client-side caching to avoid adding latency.
- Langfuse supports LLM-as-a-judge, code evaluators, user feedback, manual labeling, and custom evaluation pipelines via APIs and SDKs.
- Langfuse datasets provide test sets and benchmarks for pre-deployment testing and structured experiments.
- Langfuse includes an LLM Playground for testing prompts and model configurations, reachable directly from a bad trace result.
- Langfuse offers a public API with an OpenAPI spec, a Postman collection, and typed SDKs for Python and JS/TS.

### How it works

Langfuse runs as Langfuse Cloud or on your own infrastructure. You instrument your app with the Python or JS/TS SDKs, the @observe() decorator, or integrations such as OpenAI, LangChain, LlamaIndex, Haystack, LiteLLM, Vercel AI SDK, and Mastra. Traces go to the Langfuse server, which is built with ClickHouse. API keys and a base URL connect your app.

## How to install Langfuse

**Python SDK with OpenAI integration**

```
pip install langfuse openai
```

**JS/TS SDK (current)**

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

**Self-host locally with Docker Compose**

```
docker compose up
```

### Requirements

- The Python SDK requires Python 3.11 or later and below 4.0.
- The npm langfuse package requires Node.js 18 or later.
- Langfuse API credentials (secret and public keys) from a project.
- Docker Compose for local or VM self-hosting, or Kubernetes with Helm for production.

### First steps

1. Create a Langfuse Cloud account or self-host Langfuse, then create a new project.
2. Create new API credentials in the project settings.
3. Set LANGFUSE_SECRET_KEY, LANGFUSE_PUBLIC_KEY, and LANGFUSE_BASE_URL in a .env file, choosing the EU or US region.
4. Wrap functions with the @observe() decorator and use the Langfuse OpenAI integration, then view traces in Langfuse.

## Who Langfuse is for

- Teams debugging LLM applications and agents in production through hierarchical traces.
- Developers who want to self-host LLM observability on their own infrastructure.
- Teams versioning prompts and running evaluations and experiments on datasets.
- Projects built on LangChain, LlamaIndex, OpenAI SDK, or Vercel AI SDK that want automated instrumentation.

### Limitations

- Langfuse is MIT licensed except for the ee folders, which fall under separate terms.
- The npm package langfuse is a deprecated v3 client; new JS/TS work should use @langfuse/tracing and @langfuse/otel.
- Self-hosting with the default docker-compose.yml can exhaust disk space unless Docker log rotation is configured.
- The LlamaIndex and Haystack integrations support Python only; the LiteLLM JS/TS integration is proxy only.

## Usage data (the week of Oct 25–31, 2026)

- Board rank: #71 overall, #4 in Evals and observability, momentum score 70
- Downloads that week: 9.8M (+9% vs 4-week average)
- New GitHub stars per week (last 12 weeks): Aug 9: 415; Aug 16: 421; Aug 23: 362; Aug 30: 346; Sep 6: 292; Sep 13: 314; Sep 20: 274; Sep 27: 276; Oct 4: 299; Oct 11: 377; Oct 18: 444; Oct 25: 414

## Langfuse alternatives

| Rank | Tool | Stars | Downloads/wk |
|---|---|---|---|
| #1 | [SkillSpector](https://index.devtoolwatch.com/tools/nvidia-skillspector/) | 23.7k | – |
| #2 | [Judgeval](https://index.devtoolwatch.com/tools/judgmentlabs-judgeval/) | 1.1k | 80.2k |
| #3 | [A.I.G (AI-Infra-Guard)](https://index.devtoolwatch.com/tools/tencent-ai-infra-guard/) | 7.2k | – |
| #5 | [Opik](https://index.devtoolwatch.com/tools/opik/) | 23.1k | 709.1k |
| #6 | [promptfoo](https://index.devtoolwatch.com/tools/promptfoo/) | 26.7k | 1.2M |
| #7 | [garak](https://index.devtoolwatch.com/tools/garak/) | 9.8k | 12.9k |

## Langfuse FAQ

### Is Langfuse free and open source?

Langfuse's code is on GitHub (langfuse/langfuse), but the repository doesn't declare a standard open-source license. Check its license file before using it commercially. Its website links to a pricing page: https://langfuse.com/pricing.

### How do I install Langfuse?

Run `pip install langfuse openai`. It needs Node.js >=18. The install section above has the other options from the project's README.

### Is Langfuse still maintained?

Yes. The langfuse/langfuse repository was last updated on Oct 21, 2026, and the latest release, v4.67.0 on GitHub, came out on Oct 21, 2026.

### How popular is Langfuse?

Langfuse has 36.8k GitHub stars as of Nov 1, 2026. It gained 414 new stars in the week of Oct 25–31, 2026, against a 12-week average of 353 a week. Its main package had about 9.8M downloads that week, +9% against its own 4-week average. That made it #4 among LLM evals and observability tools on the Devtoolwatch Board.

### Langfuse vs LangChain: how do they compare?

Langfuse and LangChain are both tracked by Devtoolwatch. Langfuse has 36.8k GitHub stars and LangChain has 148.8k. In the week of Oct 25–31, 2026, Langfuse's main package had 9.8M downloads and LangChain's had 41.1M. [LangChain review](https://index.devtoolwatch.com/tools/langchain/)

### Langfuse vs MLflow: how do they compare?

Langfuse and MLflow are both tracked by Devtoolwatch as LLM evals and observability tools. Langfuse has 36.8k GitHub stars and MLflow has 28.6k. In the week of Oct 25–31, 2026, Langfuse's main package had 9.8M downloads and MLflow's had 5.2M. MLflow is an open source AI engineering platform for tracing, evaluating, monitoring, and managing agents, LLM applications, and ML models. [MLflow review](https://index.devtoolwatch.com/tools/mlflow/)

### What are the best alternatives to Langfuse?

Other LLM evals and observability tools on the Devtoolwatch Board in the week of Oct 25–31, 2026, by momentum: SkillSpector (#1), Judgeval (#2), A.I.G (AI-Infra-Guard) (#3), Opik (#5), promptfoo (#6). The alternatives table above has their numbers.

### Is Langfuse open source?

Langfuse is open source. The repository is MIT licensed except for the ee folders, and the Python SDK and npm package are MIT licensed.

### How do I use Langfuse locally?

Langfuse runs locally with Docker Compose. Clone the repository with git clone --depth=1, change into the langfuse directory, and run docker compose up. The README says this takes about 5 minutes.

### How do I use Langfuse with LangChain?

Langfuse instruments LangChain applications automatically when you pass a Langfuse callback handler to the LangChain application. This works in both Python and JS/TS.

### Does Langfuse support LLM-as-a-judge evaluation?

Langfuse supports LLM-as-a-judge evaluators, plus code evaluators, user feedback, manual labeling, and custom pipelines. You can run evaluators on production data or during experiments.

### Is Langfuse related to LangChain?

The sources do not describe Langfuse as part of LangChain. Langfuse integrates with LangChain as a framework. Since January 2026, Langfuse has been part of ClickHouse.

### How do I use the Langfuse API?

Langfuse exposes a public API with an OpenAPI spec and a Postman collection. It also provides typed SDKs for Python and JS/TS. Teams use the API to build custom LLMOps workflows.

## Sources

1. [langfuse/langfuse on GitHub](https://github.com/langfuse/langfuse)
2. [Langfuse README](https://github.com/langfuse/langfuse/blob/main/README.md)
3. [langfuse on npm](https://www.npmjs.com/package/langfuse)
4. [langfuse on PyPI](https://pypi.org/project/langfuse/)
5. [Langfuse website](https://langfuse.com)
6. [Release v4.67.0 (Oct 21, 2026)](https://github.com/langfuse/langfuse/releases/tag/v4.67.0)
7. [Release v4.66.0 (Oct 20, 2026)](https://github.com/langfuse/langfuse/releases/tag/v4.66.0)
8. [Release v4.65.0 (Oct 20, 2026)](https://github.com/langfuse/langfuse/releases/tag/v4.65.0)
9. [Hacker News: ClickHouse acquires Langfuse](https://news.ycombinator.com/item?id=46656552)
10. [Hacker News: Launch HN: Langfuse (YC W23) – OSS Tracing and Workflows to Improve LLM Apps](https://news.ycombinator.com/item?id=42441258)
11. [Hacker News: Show HN: Langfuse – Open-source observability and analytics for LLM apps](https://news.ycombinator.com/item?id=37310070)
12. [Devtoolwatch Board, the week of Oct 25–31, 2026](https://index.devtoolwatch.com/)