Island builds security software around the place many employees already work: the browser. Workers use its enterprise browser to open company applications, while administrators control access, data movement and activity logs. The Dallas company announced a $400 million Series F at a $6.4 billion valuation, led by Evolution Equity Partners.

The workflow is more concrete than another layer of security alerts. Island can block a login from an insecure device or network, stop someone from copying information into an untrusted service and add a customer-designed authentication step to a third-party application that lacks one.

Its browser is based on Chromium, the open-source foundation behind Chrome. Companies can instead apply Island’s controls through an extension for consumer browsers, while a separate endpoint client covers programs employees run outside the browser.

AI agents complicate that setup because they can move between applications, files and internal systems without following a person’s click-by-click path. Island says its platform inventories those agents and applies identity rules, access limits, data boundaries, approval gates and audit trails to their activity.

The round is financing a change in scope as much as additional growth. Island began with the enterprise browser but now spans browser extensions, endpoints, applications, networks and data, with the company pitching one policy engine and audit trail across those layers.

The new valuation is about one-third above the $4.8 billion valuation Reuters reported for Island’s 2025 round. Island employs 1,000 people and says annual recurring revenue has doubled in every fiscal year since its 2022 launch. Reuters reported that the company lists PayPal, Amazon and Pfizer among its customers.