Horizon3 hits $2B valuation with $250M Series E as AI-powered cybersecurity demand surges

Horizon3.ai just closed a $250 million Series E funding round, pushing the San Francisco-based cybersecurity startup to a roughly $2 billion valuation. The round represents a significant step up from its $100 million Series D raised in mid-2025, which was led by NEA and valued the company above $750 million.

Horizon3.ai’s NodeZero platform replaces traditional annual penetration testing with continuous, autonomous penetration testing powered by AI. Instead of a yearly checkup, the software is constantly probing your defenses, finding vulnerabilities, and validating whether your security actually works.

NodeZero has executed between 150,000 and 170,000 autonomous penetration tests and is used by more than 3,000 organizations. Annual recurring revenue grew 137% year-over-year in the first half of 2025. Total funding for Horizon3.ai now sits at approximately $428 million since the company was founded in 2019 by tech and military veterans focused on offensive security.

The company also recently launched NodeZero WebApp Pentesting on July 29, 2026, extending its autonomous testing capabilities to web applications and covering a broader range of attack vectors.

Smart contract audits, the crypto world’s version of pentesting, have long suffered from the same limitation as traditional security. A protocol gets audited before launch, maybe once more after a major upgrade, and then assumes it’s safe. Horizon3.ai’s ARR growth of 137% and valuation jump from above $750 million to roughly $2 billion in under a year reflects a decisive shift toward automation-first security strategies among enterprise buyers.

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