Arcjet
Arcjet provides runtime security for AI agents, enforcing policies at the action boundary.
- Categories
- AI and LLM security, WAF and bot protection, API security
- Based in
- San Francisco, United States
- Founded
- 2023
- Ownership
- Private
- Certifications
- SOC 2 Type 2
About Arcjet
Arcjet is an AI agent runtime security and application security platform. It protects coding agents such as Claude Code, Codex, Copilot and Cursor, and custom agents built in JavaScript, TypeScript, Python or Go. It sells to security and platform teams, engineering teams building AI agents and MCP servers, and B2B SaaS product teams. The company is Arcjet Labs, Inc., founded in 2023 by David Mytton, with a seed round led by Andreessen Horowitz and a Series A in 2025. It is remote-first with about ten staff and a hub in New York.
Products
- Shield WAFA web application firewall for blocking common attacks.
- Bot protectionDetects and blocks automated bot traffic.
- Rate limitingCaps requests per user, organisation or agent.
- Signup form protectionGuards signup forms against abuse.
- Email validationChecks email addresses for validity.
- Prompt injection detectionFinds hostile instructions in inputs and outputs before they reach a model.
Ownership and deals
- Raised $8.3m in a Series A roundInvestor Plural PlatformReport on the Arcjet funding round of October 2025 (opens in a new tab)
- Raised $8.5mReport on the Arcjet funding round of May 2025 (opens in a new tab)
- Raised $3.6m in a seed roundInvestor Andreessen HorowitzReport on the Arcjet funding round of September 2024 (opens in a new tab)
Acquisitions come from SecurityWeek's monthly M&A round-ups from 2021 onwards, from Cybersecurity Ventures' quarterly M&A reports for 2020, and a few from Wikipedia lists. Funding rounds from 2022 onwards come from Return on Security's weekly Security, Funded newsletter. These are dated to the month. A few deals added from the news are dated to the day. Smaller deals may be missing. Amounts are in US dollars.