Weights & Biases vs Langfuse
A detailed comparison to help you choose between Weights & Biases and Langfuse.
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Verdict: Langfuse wins
Langfuse scores 4.3/5, edging out Weights & Biases at 4.2/5. Engineering teams running LLM apps or agents in production who want framework-agnostic tracing and evaluation with either a cheap managed cloud or a free self-hosted stack.
Weights & Biases MLOps platform for AI model development | Langfuse Open-source LLM observability and evaluation | |
|---|---|---|
| Rating | 4.2 (1 review) | 4.3 (1 review) |
| Pricing Model | freemium | freemium |
| Starting Price | Free tier available | Free tier available |
| Best For | ML engineers and data scientists who want near-zero-friction experiment tracking with LLM evaluation under one roof, in teams small enough for Pro or ready for Enterprise. | Engineering teams running LLM apps or agents in production who want framework-agnostic tracing and evaluation with either a cheap managed cloud or a free self-hosted stack. |
| Free Tier | ||
| API Access | ||
| Team Features | ||
| Open Source | ||
| Tags | free tierteam featuresapi access | free tieropen sourceapi access |
| Visit Weights & Biases → | Visit Langfuse → |
Weights & Biases
Pros
- + Instrumenting a PyTorch loop took about ten lines and gave me usable loss curves, system metrics and sweeps within minutes
- + Free tier genuinely works for personal projects: 5 seats, 5 GB storage, and experiment tracking plus Weave tracing at $0
- + One account covers classic training runs and LLM tracing/evaluation via Weave, so I did not need a second vendor for the eval project
- + Artifacts with lineage let me version datasets and models and reconstruct which data produced which checkpoint
- + The 30 September 2026 CoreWeave Forge sign-in migration was a non-event in my account — credentials, projects and runs carried over
Cons
- - Weave ingestion overage at $0.10/MB on Pro punishes verbose LLM logging; my evaluation project blew through the 1.5 GB/month inclusion
- - Pro plans are capped at organisations under 50 employees — a growing client was moved to an Enterprise conversation mid-project
- - Four metered dimensions at once (seats, storage, ingestion, inference) make bills hard to forecast without instrumentation
- - Enterprise is quote-based with self-serve pricing stopping at Pro, so the step-up is a sales process
- - Pre-acquisition pricing write-ups (per tracked-hour tiers) are now stale and mislead buyers comparing quotes
Langfuse
Pros
- + MIT-licensed core with free, unrestricted self-hosting — only named enterprise features like audit logs and SCIM need a licence key
- + A 5-seat team at 100k traces runs roughly $69/month versus about $420/month for the main closed alternative (Panoply's independent estimate, consistent with my bills)
- + OpenTelemetry-native tracing across OpenAI SDK, LangChain, LlamaIndex, Pydantic AI, Vercel AI SDK, CrewAI and raw OTLP
- + Graduated usage pricing is transparent and cheap: worked examples on the pricing page match my own invoices (200k units on Core = $37/month)
- + Dataset-backed evaluation with the langfuse/experiment-action GitHub step let me gate prompt changes in CI on a real test set
Cons
- - v3 self-hosting needs Postgres, ClickHouse, Redis and S3 where v2 ran on one container — a four-service system to operate
- - Heavy agent traces render slowly in the UI (issue threads #10391 and #9933 match the multi-second loads I measured)
- - Online evaluations score a sample of traffic rather than everything, so rare failure modes can go unscored
- - UI-configured evaluators cannot be triggered programmatically for scheduled pipelines in my setup
- - Owned by ClickHouse, Inc. since January 2026 — licence unchanged so far, but the vendor-independence profile shifted
Frequently Asked Questions
Which is better, Weights & Biases or Langfuse?▼
Langfuse scores higher at 4.3/5 vs 4.2/5 for Weights & Biases, making it the better-rated option in our comparison.
What is the difference between Weights & Biases and Langfuse?▼
Weights & Biases: Weights & Biases tracks machine learning experiments, datasets and model versions, and compares training runs across a team. Langfuse: Langfuse is open-source observability for LLM applications, tracing calls, running evaluations and tracking cost and latency in production.
Is Weights & Biases or Langfuse more affordable?▼
Weights & Biases starts at €0/mo, Langfuse starts at €0/mo. Check the comparison table above for current pricing.
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