--- title: "fact-checker vs promptfoo" type: "comparison" canonical_url: "https://www.graphcanon.com/compare/jagilley-fact-checker-vs-promptfoo-promptfoo" tools: ["jagilley-fact-checker", "promptfoo-promptfoo"] --- # fact-checker vs promptfoo *GraphCanon updated Jul 12, 2026* ## Verdict Pick fact-checker if `fact-checker` utilizes prompt chaining in Jupyter Notebook to fact-check Language Model outputs, enhancing the accuracy and reliability of responses; pick promptfoo if promptfoo is a specialized tool for evaluating and testing AI-generated outputs like prompts, agents, and RAGs (Retrieval-Augmented Generation) through methods such as red teaming, pentesting, and vulnerability scanning. [fact-checker](https://github.com/jagilley/fact-checker) reports 308 GitHub stars, 40 forks, and 0 open issues, last pushed Oct 23, 2023. [promptfoo](https://promptfoo.dev) has 23k stars, 2.1k forks, and 413 open issues, last pushed Jul 11, 2026. Figures are from public GitHub metadata via [fact-checker's repository](https://github.com/jagilley/fact-checker) and [promptfoo's repository](https://github.com/promptfoo/promptfoo). | | [fact-checker](/tools/jagilley-fact-checker.md) | [promptfoo](/tools/promptfoo-promptfoo.md) | | --- | --- | --- | | Tagline | Fact-checking LLM outputs with self-ask | Test your prompts, agents, and RAGs. Red teaming/pentesting/vulnerability scanning for AI. Compare performance of GPT, Claude, Gemini, DeepSeek, and more. Simple declarative configs with command line | | Stars | 308 | 23,155 | | Forks | 40 | 2,071 | | Open issues | 0 | 413 | | Language | Jupyter Notebook | TypeScript | | Adopt for | `fact-checker` utilizes prompt chaining in Jupyter Notebook to fact-check Language Model outputs, enhancing the accuracy and reliability of responses. | Promptfoo is a specialized tool for evaluating and testing AI-generated outputs like prompts, agents, and RAGs (Retrieval-Augmented Generation) through methods such as red teaming, pentesting, and vulnerability scanning. | | Persona | - | - | | Runtime | - | - | | License | - | Promptfoo uses an MIT license which allows free use, modification, distribution, and commercial exploitation under the condition that appropriate attribution is given to the original authors. | | Categories | Evaluation & Observability | AI Agents, LLM Frameworks, Vector Databases | ## Trust and health _Sourced signals - not a safety guarantee. No winner column._ | | [fact-checker](/tools/jagilley-fact-checker.md) | [promptfoo](/tools/promptfoo-promptfoo.md) | | --- | --- | --- | | Maintenance | Dormant (18%) | Very active (96%) | | Days since push | 991d | 0d | | Open issues (now) | 0 | 413 | | Owner type | User | Organization | | Full report | [trust report](/tools/jagilley-fact-checker/trust.md) | [trust report](/tools/promptfoo-promptfoo/trust.md) | ## Shared compatibility - **Python**: [fact-checker](/tools/jagilley-fact-checker.md) - Python runtime; [promptfoo](/tools/promptfoo-promptfoo.md) - Python runtime ## Decision facts: fact-checker - **Pricing:** unknown - The licensing information for `fact-checker` is unclear, indicating that further investigation into its legal usage might be required before implementation. - **Requirements:** Requires Python and possibly Jupyter Notebook environment for running the provided IPython notebook script or command-line script. - **Adopt for:** `fact-checker` utilizes prompt chaining in Jupyter Notebook to fact-check Language Model outputs, enhancing the accuracy and reliability of responses. ## Decision facts: promptfoo - **Pricing:** freemium - The basic version of Promptfoo is freely available due to its open-source nature under MIT licensing. Advanced features may require a paid plan from future commercial offerings. - **Requirements:** Requires TypeScript runtime and relevant node.js or deno setup to run.; May need additional configuration for CI/CD integration, depending on the build ecosystem. - **Adopt for:** Promptfoo is a specialized tool for evaluating and testing AI-generated outputs like prompts, agents, and RAGs (Retrieval-Augmented Generation) through methods such as red teaming, pentesting, and vulnerability scanning. - **License detail:** Promptfoo uses an MIT license which allows free use, modification, distribution, and commercial exploitation under the condition that appropriate attribution is given to the original authors. ## Choose when ### Choose fact-checker if… - fact-checker is primarily Jupyter Notebook; promptfoo is TypeScript. - Pricing: The licensing information for `fact-checker` is unclear, indicating that further investigation into its legal usage might be required before implementation.. - Requirements: Requires Python and possibly Jupyter Notebook environment for running the provided IPython notebook script or command-line script.. - Tags unique to fact-checker: fact-checking, prompt-chaining, python. - Also covers Evaluation & Observability. - - When you need to verify the accuracy of assumptions made by a Language Model’s initial response through self-ask methodologies. ### Choose promptfoo if… - promptfoo is primarily TypeScript; fact-checker is Jupyter Notebook. - Pricing: The basic version of Promptfoo is freely available due to its open-source nature under MIT licensing. Advanced features may require a paid plan from future commercial offerings.. - Requirements: Requires TypeScript runtime and relevant node.js or deno setup to run.; May need additional configuration for CI/CD integration, depending on the build ecosystem.. - Tags unique to promptfoo: ci, ci-cd, cicd, evaluation. - Also covers AI Agents, LLM Frameworks, Vector Databases. - promptfoo ships Docker support for self-hosted deployment. - When you need to assess the robustness of your RAG systems against potential vulnerabilities. ## When NOT to use fact-checker - - If an immediate answer is required without the step-by-step reassessment process, as `fact-checker` involves sequential validation that could be time-consuming. - - In situations where real-time interaction is critical and a delay from additional self-interrogation steps would not be beneficial for user experience. ## When NOT to use promptfoo - When you are specifically looking for general-purpose evaluation tools that do not have the focused depth on security and vulnerability provided by Promptfoo. - If your workflow or project cannot support TypeScript, as this tool is built in TypeScript and might require additional setup for non-TypeScript environments. ## Common questions ### What is the difference between fact-checker and promptfoo? fact-checker: Fact-checking LLM outputs with self-ask. promptfoo: Test your prompts, agents, and RAGs. Red teaming/pentesting/vulnerability scanning for AI. Compare performance of GPT, Claude, Gemini, DeepSeek, and more. Simple declarative configs with command line . See the comparison table for live GitHub stats and shared categories. ### When should I choose fact-checker over promptfoo? Choose fact-checker over promptfoo when fact-checker is primarily Jupyter Notebook; promptfoo is TypeScript; Pricing: The licensing information for `fact-checker` is unclear, indicating that further investigation into its legal usage might be required before implementation.; Requirements: Requires Python and possibly Jupyter Notebook environment for running the provided IPython notebook script or command-line script.; Tags unique to fact-checker: fact-checking, prompt-chaining, python; Also covers Evaluation & Observability; - When you need to verify the accuracy of assumptions made by a Language Model’s initial response through self-ask methodologies. ### When should I choose promptfoo over fact-checker? Choose promptfoo over fact-checker when promptfoo is primarily TypeScript; fact-checker is Jupyter Notebook; Pricing: The basic version of Promptfoo is freely available due to its open-source nature under MIT licensing. Advanced features may require a paid plan from future commercial offerings.; Requirements: Requires TypeScript runtime and relevant node.js or deno setup to run.; May need additional configuration for CI/CD integration, depending on the build ecosystem.; Tags unique to promptfoo: ci, ci-cd, cicd, evaluation; Also covers AI Agents, LLM Frameworks, Vector Databases; promptfoo ships Docker support for self-hosted deployment; When you need to assess the robustness of your RAG systems against potential vulnerabilities. ### When should I avoid fact-checker? - If an immediate answer is required without the step-by-step reassessment process, as `fact-checker` involves sequential validation that could be time-consuming. - In situations where real-time interaction is critical and a delay from additional self-interrogation steps would not be beneficial for user experience. ### When should I avoid promptfoo? When you are specifically looking for general-purpose evaluation tools that do not have the focused depth on security and vulnerability provided by Promptfoo. If your workflow or project cannot support TypeScript, as this tool is built in TypeScript and might require additional setup for non-TypeScript environments. ### Is fact-checker or promptfoo more popular on GitHub? promptfoo has more GitHub stars (23,155 vs 308). Stars measure visibility, not whether either tool fits your constraints. ### Are fact-checker and promptfoo open source? Yes - both are open-source projects on GitHub. ### Where can I find alternatives to fact-checker or promptfoo? GraphCanon lists graph-backed alternatives at [fact-checker alternatives](/tools/jagilley-fact-checker/alternatives) and [promptfoo alternatives](/tools/promptfoo-promptfoo/alternatives) ([fact-checker markdown twin](/tools/jagilley-fact-checker/alternatives.md), [promptfoo markdown twin](/tools/promptfoo-promptfoo/alternatives.md)), ranked by typed relationship edges rather than popularity votes. ### Is there a machine-readable version of this comparison? Yes. The markdown twin at [this comparison](/compare/jagilley-fact-checker-vs-promptfoo-promptfoo.md) mirrors this page for agents and LLM crawlers, with the same stats table and FAQ answers. ### Which is better maintained, fact-checker or promptfoo? fact-checker: Dormant. promptfoo: Very active. Compare maintenance labels, days since push, and release cadence in the trust section below - stars alone do not measure maintenance. ### Where are the full trust reports for fact-checker and promptfoo? GraphCanon publishes per-repo trust reports with dated maintenance, provenance, and scan summaries: [fact-checker trust report](/tools/jagilley-fact-checker/trust); [promptfoo trust report](/tools/promptfoo-promptfoo/trust). --- **Machine-readable endpoints** - JSON: [`/api/graphcanon/graph?tool=jagilley-fact-checker`](/api/graphcanon/graph?tool=jagilley-fact-checker) - LLM index: [/llms.txt](/llms.txt) - Full corpus: [/llms-full.txt](/llms-full.txt) _GraphCanon - The knowledge graph for AI development. https://www.graphcanon.com/_