Promptfoo Raises $18.4 Million Series A to Build Definitive AI Security Stack

Led by Insight Partners with participation from Andreessen Horowitz, funding will accelerate development of the widely adopted AI security testing solution

SAN FRANCISCO, July 29, 2025 /PRNewswire/ -- Promptfoo, the widely adopted open‑source framework for AI red‑teaming and security testing, today announced an $18.4 million Series A financing led by global software investor Insight Partners, with participation from existing investor Andreessen Horowitz.

Founded in 2024, Promptfoo is steadily gaining recognition as an emerging standard for robust AI security testing, with over 100,000 developers using its open source tools and adoption by more than 30 Fortune 500 companies. The platform helps developers and security teams secure large language models (LLMs) and generative AI applications by detecting and mitigating risks like prompt injection, data leakage, and insecure tool use. Its commercial enterprise solution, launched just a year ago, is trusted by leading retailers, telecoms, and financial institutions to securely deploy AI systems.

The funding comes at a critical point for enterprise AI adoption. As companies move beyond proof-of-concepts to production deployments, the complexity and risk profile of AI systems has grown exponentially.

"AI security has become the largest blocker to enterprises shipping generative AI applications to end users," said Ian Webster, CEO and co-founder of Promptfoo. "Architectures like RAG, agents, and most recently MCP have expanded what's possible with AI, but they've dramatically increased the attack surface."

Promptfoo's platform stands apart as one of the only AI-security solutions that closes the loop from discovery to resolution. It embeds automated red-team tests directly into the build and release process, pairs findings with clear, actionable remediation guidance, and feeds results into existing vulnerability-management workflows. This end-to-end automation—spanning attack objective generation, exploit search, and regression testing—gives security and engineering teams a single, continuous workflow for hardening today's complex agentic systems, establishing Promptfoo as a leading choice for organizations aiming to deploy AI securely at scale.

"Promptfoo has created what we believe to be a category-defining product," said Ganesh Bell, Managing Director at Insight Partners. "The layers of The Next Stack built around AI are clearly emerging beyond LLMs, and Promptfoo is a critical part of that evolution—especially in the race to enable intelligence-first design and secure Enterprise AI. Serious enterprises deploying AI will need comprehensive security testing, and Promptfoo's combination of technical depth, open source adoption, and enterprise traction positions them perfectly to capture this massive market opportunity. We're thrilled to partner with them as they help build the full AI security suite."

The funding will fuel Promptfoo's expansion as it moves to establish the industry standard for enterprise AI security. The company will scale its team and accelerate platform development to meet demand from Global 2000 companies seeking comprehensive solutions to secure their AI deployments.

"When we first invested in Promptfoo, we recognized that AI security would become mission-critical for every enterprise," said Zane Lackey, General Partner at Andreessen Horowitz. "In just one year, they've validated that thesis and then some. This additional investment reflects our conviction that they'll define how companies approach AI security for years to come."

About Promptfoo

Promptfoo is the most widely adopted open source AI security testing platform, enabling enterprises to identify and remediate vulnerabilities in their AI systems before deployment. Founded in 2024, the company's tools are used by over 100,000 developers worldwide, while its enterprise platform secures AI applications for Fortune 500 companies across retail, telecommunications, finance, and media. Learn more at [Promptfoo.dev].

About Insight Partners

Insight Partners is a global software investor partnering with high-growth technology, software, and Internet startup and ScaleUp companies that are driving transformative change in their industries. As of December 31, 2024, the firm has over $90B in regulatory assets under management. Insight Partners has invested in more than 800 companies worldwide and has seen over 55 portfolio companies achieve an IPO. Headquartered in New York City, Insight has offices in London, Tel Aviv, and the Bay Area. Insight's mission is to find, fund, and work successfully with visionary executives, providing them with tailored, hands-on software expertise along their growth journey, from their first investment to IPO. For more information on Insight and all its investments, visit insightpartners.com or follow us on X @insightpartners.

SOURCE Promptfoo