Fly.io sells $23.2 million in new equity, SEC filing shows
The filing lists five investors and directors from a16z and Dell, but leaves the buyers, round label and valuation undisclosed.
By Ryan Merket · Published
Why it matters
Fly.io has secured its first disclosed capital since 2023 while funding an owned-hardware cloud and a new AI-agent sandbox product. The filing confirms $23.2 million sold but withholds the valuation and investor identities.
Fly.io co-founder and CEO Kurt Mackey (@mrkurt) has brought in $23.2 million through a new equity offering, according to an SEC Form D filed July 22nd.
The Fly.io filing sets a target of $24,999,937, leaving $1,799,992 available to sell. The first sale occurred July 7th, two weeks before Fly.io disclosed the financing. Five investors had participated by the filing date.
Fly.io did not identify those investors, label the financing as a venture round or disclose a valuation. The filing also provides no general use of proceeds. Fly.io is selling equity under Rule 506(b), an exemption that permits private offerings to accredited investors without a public solicitation. No broker commissions or finder's fees were reported.
Matthew Cunningham, identified as Fly.io's treasurer, signed the filing. Mackey is listed as a director, alongside former Docker CEO Scott Johnston and investors Martin Casado and Daniel Docter.
Five investors, no names
Casado, who leads infrastructure investing at Andreessen Horowitz, and Daniel Docter (@DanielDocter), a managing director at Dell Technologies Capital, appear as Fly.io directors in the Form D. Their inclusion does not establish that a16z or Dell participated in the new offering. Form D identifies directors and executive officers separately from the investor count, and it does not name the five buyers.
Both investors have long-standing ties to Fly.io. Andreessen Horowitz led Fly.io's $25 million Series B in 2022, with participation from Dell Technologies Capital, Intel Capital, Initialized Capital and PlanetScale CEO Sam Lambert. Fly.io also disclosed at the time that it had previously raised a $12 million Series A led by Intel Capital.
In June 2023, Fly.io raised a $70 million Series C led by EQT Ventures, with a16z, Dell Technologies Capital and Intel Capital participating. Bloomberg reported that the Series C valued Fly.io at $467 million. Fly.io's own funding announcement did not disclose a valuation.
Adding the $23.2 million sold in the current offering to the Series A, B and C figures brings Fly.io's publicly reported or filed financing to about $130.2 million. The new filing gives no indication whether the latest shares were priced above or below the 2023 valuation.
Mackey's capital-intensive cloud bet
Mackey built Fly.io around a direct challenge to the dominant public-cloud architecture: applications should run near their users, while developers should be able to deploy them without managing the underlying geographic complexity.
Before Fly.io, Mackey co-founded hosted database provider MongoHQ, later renamed Compose, and sold it to IBM in 2015. He subsequently took Fly.io through Y Combinator's Winter 2020 batch despite already having an exit behind him.
Fly.io differs from software-only deployment platforms because it operates its own servers in colocation facilities. Fly.io packages containerized applications into hardware-isolated virtual machines and routes traffic over a global network. Its Fly Machines can be created, cloned across regions, stopped and restarted through an API or command-line interface.
That model requires capital before customer usage produces a return. In Fly.io's 2023 financing post, Mackey said owning the hardware was central to making margins work, while adding regions, improving reliability and developing storage and security capabilities required continued investment. Fly.io currently uses usage-based infrastructure pricing, with paid support and compliance packages layered on top, according to its pricing page.
Fly.io declined to disclose its revenue range in the new Form D. Current revenue, active customer counts and headcount therefore remain outside the filing. Fly.io describes itself as remote-first with no central office, even though the SEC document lists a San Francisco address as its principal place of business.
New capital follows an AI infrastructure push
The financing arrives after Mackey pushed Fly.io beyond application hosting and deeper into infrastructure for AI coding agents. In January, Fly.io launched Sprites, persistent Linux environments designed to execute AI-generated or otherwise untrusted code inside isolated Firecracker virtual machines.
Sprites use directly attached storage that syncs to object storage, support checkpoint and restore, and pause their compute when idle. Fly.io positions them as disposable computers that retain their files and configuration between sessions. The product targets a growing infrastructure problem for agent developers: giving software-writing models broad access to a working computer without exposing a shared host or production environment.
Mackey wrote in Fly.io's Sprites launch post that the architecture required a new storage stack and different orchestration from Fly Machines. Fly.io had spent years adapting its production-application infrastructure for sandbox workloads before building a separate product around how coding agents actually operate.
The Form D does not connect the proceeds to Sprites or any other product. The timing nevertheless puts fresh capital behind Fly.io as it maintains a hardware fleet for its established cloud service while opening a second workload category around AI agents. Both depend on Fly.io's ability to turn infrastructure ownership into better economics than renting equivalent capacity from Amazon Web Services, Google Cloud or Microsoft Azure.
At $23.2 million sold, the offering is modest beside the $500 million-plus financings that have absorbed most US venture dollars this year. RuntimeWire reported in May that those mega-round recipients accounted for about 80% of US venture investment through April. Fly.io's filing shows capital is still available for infrastructure founders outside that small group, although the undisclosed valuation leaves the price of that capital unknown.