OpenRouter is a unified API and marketplace for 📝large language models that routes a single request across hundreds of models from providers such as OpenAI, 📝Anthropic, 📝Google, and Mistral, letting developers compare and switch between them by cost, speed, and capability.
Founded in 2023 by OpenSea co-founder Alex Atallah and Louis Vichy, OpenRouter exposes a single OpenAI-compatible endpoint so developers can call many models without rewriting code, with automatic fallbacks and pay-as-you-go billing aggregated across providers. It publishes public model rankings and usage data, positioning itself as a neutral point of comparison in a fragmented model market. By 2025 the platform had grown from a developer backend into a broader product, reporting annualized inference spend above $100 million and raising roughly $40 million in venture funding led by Andreessen Horowitz and Menlo Ventures. Its role as an aggregator also makes it a de facto arbiter of model discovery—shaping which models developers most readily find, test, and adopt.