Promptfoo agrees to be acquired by OpenAI as AI security testing moves into the spotlight

AI testing platform Promptfoo will join OpenAI following an acquisition agreement announced by the company’s founders, bringing red teaming and evaluation tools used by hundreds of thousands of developers closer to the infrastructure behind large language models.

AI testing platform Promptfoo has agreed to be acquired by OpenAI, according to an announcement from the company’s founders. The deal signals growing focus on security testing, evaluation, and governance as organizations deploy generative AI systems at scale.

Promptfoo says its platform is used by more than 350,000 developers and teams at over 25 percent of Fortune 500 companies to test AI systems for safety, security, and behavioral risks before deployment.

The company also confirmed that Promptfoo will remain open source and continue supporting existing users and customers following the acquisition.

Platform built to test and secure AI applications

Promptfoo was founded in 2024 by Ian Webster and Michael D'Angelo to help developers systematically test AI applications.

In the acquisition announcement, the founders write:

“We founded Promptfoo in 2024 to make it easy for developers to systematically test their AI applications. We quickly realized that adversarial tests for security, safety, and other behavioral risks were the biggest blockers to shipping AI, especially at large enterprises.”

They add that adoption grew quickly as companies began deploying generative AI systems into production environments: “More than 350k developers have used it, 130k are active each month, and teams at more than 25% of the Fortune 500 rely on it.”

The founders say the acquisition will allow the platform’s testing and evaluation capabilities to integrate more closely with AI model infrastructure: “We are joining OpenAI so that the security, evaluation, and compliance platform we've built - and the frontline experience behind it - can have the greatest impact on how teams build and deploy AI.

“At OpenAI, we'll improve and integrate Promptfoo's core tech within the model and infrastructure layers, so teams can catch vulnerabilities early and ship secure AI from the start.”

Open source tools will continue after the deal

Promptfoo says its open-source suite will continue to operate after the acquisition and will remain compatible with multiple AI providers and models: “OpenAI gives our work more resources and access to research at the model and inference layers that supercharge our goal of helping everyone ship secure, reliable AI.”

The founders also say the team will continue working with users and customers during the transition: “The team will continue working with customers and users to ensure continuity of service and support.”

Investors highlight growing demand for AI security tools

Promptfoo is backed by investors including Insight Partners and Andreessen Horowitz, both of which supported the company during its early growth.

Ganesh Bell, Managing Director at Insight Partners, comments: “Promptfoo built what we believe is a category-defining platform for AI evaluation and security. As enterprises deploy more complex AI systems, rigorous testing, red teaming, and evaluation become foundational. Ian, Michael, and the team built something essential.”

Zane Lackey, General Partner at Andreessen Horowitz, adds: “We believed early that AI security would become mission-critical, and Promptfoo validated that thesis in a big way. Ian, Michael, and the team built a platform that helps organizations find and fix AI risks before they ship, all while building in the open and earning deep trust from developers and enterprises alike. We're incredibly excited to see their continued impact on the future of AI security.”

The companies say the transaction is subject to customary closing conditions.

ETIH Innovation Awards 2026

The ETIH Innovation Awards 2026 are now open and recognize education technology organizations delivering measurable impact across K–12, higher education, and lifelong learning. The awards are open to entries from the UK, the Americas, and internationally, with submissions assessed on evidence of outcomes and real-world application.