Promptfoo announced an $18.4 million Series A on July 29, 2025, led by Insight Partners, with Andreessen Horowitz participating. The company said it would use the funding to advance its AI security testing products. A later development changed the company’s story: Promptfoo and OpenAI announced an acquisition agreement on March 9, 2026. OpenAI said the agreement remained subject to customary closing conditions, so the announcement does not establish that the acquisition has closed.
Who led Promptfoo’s $18.4 million Series A?
Promptfoo announced the Series A on July 29, 2025. Insight Partners led the round, and Andreessen Horowitz (a16z) participated, according to Promptfoo’s announcement. The company described the financing as support for developing its AI security testing solution; the announcement did not disclose a company valuation.
How does the Series A compare with Promptfoo’s earlier funding?
Promptfoo previously announced a $5 million seed round in July 2024, led by Andreessen Horowitz, in its seed announcement. The two disclosed rounds add up to $23.4 million. That total covers only these announced rounds and does not establish Promptfoo’s total lifetime funding.
| Announcement | Amount | Lead investor | Other participation stated |
|---|---|---|---|
| Seed round, July 2024 | $5 million | Andreessen Horowitz | Not stated in Promptfoo’s announcement |
| Series A, July 2025 | $18.4 million | Insight Partners | Andreessen Horowitz |
What does Promptfoo’s AI security platform do?
Promptfoo describes its offering as an open-source framework and an enterprise platform for red-teaming and security testing AI applications. In its Series A announcement, the company said its tools test systems such as AI agents, retrieval-augmented generation applications, and Model Context Protocol servers. It described automated testing integrated into development workflows, intended to help teams find issues before deployment.
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The risks named in the announcement include prompt injection, data leakage, and insecure tool use. These are Promptfoo’s stated product goals and capabilities, not independently measured proof that the platform prevents those risks or makes a system secure.
What adoption figures did Promptfoo report?
In its July 2025 Series A announcement, Promptfoo reported that more than 125,000 developers used its open-source framework. The same post gives differing figures for Fortune 500 customers in separate sections: one says more than 30 companies ran the platform in production, while another says 40 or more. Those are historical company-reported figures, not audited counts or current 2026 usage numbers.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What happened after the funding announcement?
On March 9, 2026, Promptfoo and OpenAI announced an agreement for OpenAI to acquire Promptfoo. OpenAI’s announcement said the acquisition was subject to customary closing conditions and described plans to integrate Promptfoo’s capabilities with Frontier. Promptfoo’s announcement said the project would remain open source and that the company would continue serving users and customers.
The reviewed announcements establish an agreement and intended integration, not a completed transaction. They also do not disclose an acquisition price. The $18.4 million Series A amount is not a basis for estimating either the purchase price or Promptfoo’s valuation.
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