Modal, a startup that provides cloud computing infrastructure for AI applications, has raised $750 million in a Series D funding round at a $15.75 billion post-money valuation after crossing $1 billion in annualized run rate.

Accel led the round, while Kleiner Perkins joined as a new investor, Modal said Wednesday. Existing investors Menlo Ventures, General Catalyst, Redpoint, Lux Capital, Amplify Partners and Bain Capital Ventures also participated.

Modal's valuation has more than tripled in five months. The startup raised $355 million in Series C at a $4.65 billion post-money valuation in May, when its annualized run rate had passed $300 million.

The latest round brings Modal's total funding to more than $1.2 billion, including an $87 million Series B, a $16 million Series A and a $7 million seed round.

Founded in 2021 by Erik Bernhardsson and Akshat Bubna, Modal lets developers run AI models, agents and other computing tasks in the cloud without setting up and managing the underlying servers themselves.

Modal has built its own technology to manage computing, including systems for running software, scheduling tasks and connecting servers. Its computing capacity now covers more than 20 cloud providers.

Modal said usage has tripled since May and grown more than 15 times compared with a year ago.

Developers use Modal to train AI models and run them after training, a process known as inference.

"AI has unlocked a whole new set of software capabilities," Bernhardsson said. "The old stack doesn't quite fit them. They need different building blocks and a new way to think about infrastructure."

Modal launched its Sandboxes product in 2023 after seeing developers use large language models to generate and run code.

Sandboxes let AI agents run code in a separate environment without affecting the customer's main system. They are used for AI coding tools, reinforcement learning, and software development.

Modal said Sandboxes alone have reached a $300 million annualized run rate. The startup has created nearly 3 billion Sandboxes and can run up to 1 million at the same time.

TypeSafe AI's Jev model processed 1 trillion tokens on Modal during its first three days, according to the startup. DoorDash uses Modal to move AI applications from testing into production, while Cognition, Ramp, Linear and Hebbia use it for AI agents, Modal said.

Runway uses the platform for video generation. Physical Intelligence, Generalist AI and 1X use Modal for robotics, while Chai Discovery and Achira use it for drug research. Other customers include AI music startup Suno.

Modal has grown from more than 120 employees in May to over 200 across New York, San Francisco, and Stockholm. The startup is hiring for additional roles.