OpenSea co-founder Alex Atallah raises $40 million for AI startup OpenRouter

OpenRouter, headed up by a former OpenSea co-founder, has raised $40 million in combined seed and Series A funding to accelerate the development of its large language models aggregator platform.

The financing was led by Andreessen Horowitz and Menlo Ventures, with participation from Sequoia and prominent industry angels, according to a press release. The company is now valued at $500 million, the Wall Street Journal reported, citing a person familiar.

OpenRouter is an AI infrastructure startup that acts as a marketplace and routing platform for LLMs. It aggregates access to hundreds of models from providers like OpenAI, Anthropic, and Meta, and automatically directs user prompts to the most suitable model based on cost, speed, accuracy, and privacy needs.

“AI stacks are fragmenting. OpenRouter is unifying them with one API, one contract, and industry-leading uptime — exactly the kind of infrastructure play that defines new categories,” Andreessen Horowitz General Partner Anjney Midha said.

Developers pay with credits to run inferences, and OpenRouter takes a small fee per request, aiming to simplify model selection and optimization in an increasingly crowded AI landscape.

“Inference is the fastest-growing cost for forward-looking companies, and it’s often coming from 4 or more different models. The sophisticated companies have run into these problems already, and built some sort of in-house gateway. But they’re realizing that making LLM’s ‘just work’ isn’t an easy problem. They’re ripping out home-grown solutions and bringing in OpenRouter so they can focus on their domain-specific problems, and not on LLM integration,” OpenRouter co-founder and CEO Alex Atallah said. “This round lets us keep shipping at the speed developers expect while delivering the uptime, privacy, and IT guarantees that enterprises demand.”

Atallah previously co-founded OpenSea with CEO Devin Finzer in 2018 and served as Chief Technology Officer during its rapid growth phase. He stepped down from the NFT marketplace in July 2022 to “build something from zero to one,” while remaining on its board.

The timing of Attalah’s exit coincided with the end of the NFT hype cycle, and the crypto niche has struggled to regain its activity levels of 2021 and 2022. Later, Atallah co-founded OpenRouter with Louis Vichy.

Gaining traction

Founded in 2023, OpenRouter claims to have rapidly scaled to over $100 million in annualized inference spend, up from just $10 million in late 2024, with more than a million developers using its API since its launch. With customers that range from early-stage startups to large multinationals, it routes AI traffic across an ecosystem that includes integrations with Microsoft VSCode, Zapier, and Cloudflare. Its close partnership with leading AI labs, including OpenAI, has enabled it to offer early access to frontier models like GPT-4.1.

“OpenRouter has been an early and enthusiastic collaborator on OpenAI models like GPT-4.1,” Tabarak Khan, Technical Success at OpenAI, said. “Their diverse and active developer community has shared valuable feedback on how our models perform in practice. We’re excited to keep building alongside them as they help the world discover and use the latest LLMs.”