promptfoo vs W&B Weave
Which should you use? A side-by-side look at what each one does, who it suits, what it costs, how hard it is to set up, and where each falls short.
Open source · MIT
CLI and library for testing LLM prompts and red-teaming AI apps, with declarative configs.
AI tool · Freemium
Weights & Biases' toolkit for tracing, evaluating and comparing LLM application versions.
The short answer
Choose promptfoo if you need…
- Developers building apps on top of LLM APIs who want repeatable prompt tests
- Teams comparing several models side by side on the same prompts
- People who want to run automated LLM checks in CI/CD pipelines
- Teams looking for a local, command-line way to scan LLM apps for security issues
Choose W&B Weave if you need…
- Teams already on Weights & Biases
- Evaluation leaderboards across versions
Side-by-side
| promptfoo | W&B Weave | |
|---|---|---|
| Type | Dev tool | Prompting · Evaluation & observability |
| Price | Free and open source | Freemium |
| Licence | MIT | — |
| GitHub stars | 26.7k | — |
| Setup difficulty | Intermediate | — |
| How you get it | Install with a package manager | — |
| Platforms | CLI, Web | Web, API |
| Works with | GitHub, OpenAI, Anthropic | OpenAI, Anthropic |
| Main language | TypeScript | — |
| Last code update | 4 days ago | — |
| Hands-on tested by us | — | Not yet |
| Last checked | — | 2026-10-29 |
What each one is
promptfoo
Promptfoo is a command-line tool and library for evaluating LLM-based apps. You write a declarative config listing prompts, models, and test cases, then run it to compare outputs across providers such as OpenAI, Anthropic, and Ollama. It also includes red-teaming features that scan AI apps for security vulnerabilities.
W&B Weave
Weights & Biases' toolkit for tracing, evaluating and comparing LLM application versions. Natural fit for ML teams using W&B. Feels heavier than lighter-weight tools for small projects.
Best for
promptfoo
- Developers building apps on top of LLM APIs who want repeatable prompt tests
- Teams comparing several models side by side on the same prompts
- People who want to run automated LLM checks in CI/CD pipelines
- Teams looking for a local, command-line way to scan LLM apps for security issues
W&B Weave
- Teams already on Weights & Biases
- Evaluation leaderboards across versions
Strengths
promptfoo
- The README states that evals run locally and prompts never leave your machine
- Works with many providers and any LLM API, according to the README
- Has a large community with about 26,500 stars and an MIT license
W&B Weave
- Automatic call tracing
- Evaluation framework
- Version comparison
- Scorers and guardrails
Not ideal for
promptfoo
- People who want a no-code, point-and-click tool, since the workflow centers on the command line and config files
- Projects that do not call any LLM APIs, because there is nothing for it to evaluate
- Anyone who needs a guaranteed security audit, since the README describes scanning as a tool rather than a complete assurance
W&B Weave
—
Trade-offs
promptfoo
- The README says the project is now part of OpenAI, which may matter to some users evaluating independence
- Requires API keys for most providers, which means usage costs from those providers
- Some claims in the README, such as usage by OpenAI and Anthropic and serving 10M+ users, are not independently verified here
W&B Weave
—
Getting started
promptfoo
Install globally with npm
npm install -g promptfooCreate a starter example
promptfoo init --example getting-startedW&B Weave
Get started on the W&B Weave websiteFrequently asked questions
What is the difference between promptfoo and W&B Weave?
promptfoo: CLI and library for testing LLM prompts and red-teaming AI apps, with declarative configs. W&B Weave: Weights & Biases' toolkit for tracing, evaluating and comparing LLM application versions. promptfoo suits developers building apps on top of llm apis who want repeatable prompt tests, while W&B Weave suits teams already on weights & biases.
Are promptfoo and W&B Weave free?
promptfoo: Free and open source. W&B Weave: Freemium.
What are other alternatives to promptfoo and W&B Weave?
Other options people compare them with include Composio, Prompt flow, Portkey AI Gateway, lm-evaluation-harness, book-to-skill.
Keep comparing
Built from our catalogue entries for both products: open-source details come from each project's README (AI-assisted, refreshed weekly) and GitHub data; AI-tool details are editorial. Spotted something wrong? Let us know from either product's page.