Promptfoo

Promptfoo is an open-source AI security and evaluation platform founded in 2024 by Ian Webster and Michael Meijer, headquartered in San Francisco, California. The company builds tooling that enables developers and security teams to test, evaluate, and red-team large language models, RAG pipelines, and AI agents prior to production deployment.

The platform's core product allows users to run automated adversarial probes against LLM-based applications to surface vulnerabilities such as prompt injection, jailbreaks, data leakage, and other failure modes. Promptfoo is distributed as an open-source tool with an enterprise tier, and has been adopted by engineering and security teams seeking structured evaluation workflows for AI systems.

Prompfoo was acquired by OpenAI in March 2026. Prior to the acquisition, the company had raised early-stage funding and operated with a small team. The open-source repository on GitHub accumulated significant community adoption, contributing to the company's visibility in the AI security space.