LMArena, a startup that helps artificial intelligence developers benchmark their models’ output quality, has raised $150 million in early-stage funding.

The company announced the Series A investment today. The round was led by Felicis and UC Investments, the University of California system’s asset management arm. LMArena was founded in 2023 by two UC Berkeley researchers.

The round also drew contributions from Andreessen Horowitz, The House Fund, LDVP, Kleiner Perkins, Lightspeed Venture Partners and Laude Ventures. Many of the firms on the list also backed LMArea’s $100 million seed round in May. The company disclosed that its valuation has tripled in the seven months since to $1.7 billion.

AI benchmarks usually comprise sample prompts and correct answers to those prompts. To test an AI model’s output quality, developers provide it with the sample prompts and then compare the model’s responses to the correct answers. The percentage of the questions that the model answers accurately serves as a measure of its performance.

In practice, AI benchmarks don’t always provide an accurate picture of model quality. One of the reasons is a phenomenon called data contamination. It occurs when a model finds an existing answer to a benchmark question in an external source.

Officially Arena Intelligence Inc., LMArena operates a cloud platform that helps AI developers mitigate benchmark quality issues such as data contamination. Instead of relying on static question sets to evaluate AI models, the platform uses a continuously refreshed set of prompts. Those prompts are crowdsourced from consumers.

LMArena’s platform provides a chatbot interface that enables users to search the web, generate code and perform other tasks. It sends each prompt to two different AI models and displays the algorithms’ output side-by-side. From there, the user selects the best prompt response. This feedback is used to benchmark neural networks’ performance.

It then uses the data it collects to power a regularly updated ranking of top-performing AI models. Gemini 3 Pro, a reasoning model that Google LLC released in November, is currently at the top of the list. It’s followed by a scaled-down version of the algorithm called Gemini 3 Flash and xAI Corp.’s Grok 4.1.

AI developers use the company’s leaderboard to collect feedback on new models before broadly releasing them. OpenAI Group PBC, for example, tested GPT-5 on LMArena under the codename “summit” before its release. Additionally, LMArena provides AI developers with research datasets that can be used for tasks such as mapping out model jailbreaking tactics.

“We cannot deploy AI responsibly without knowing how it delivers value to humans,” said LMArena co-founder and Chief Executive Officer Anastasios Angelopoulos. “To measure the real utility of AI, we need to put it in the hands of real users.”

Today’s funding round comes about four months after the company launched its first commercial service. AI Evaluations, as the offering is called, helps AI developers assess their models’ using feedback from LMArena users. In addition to evaluation results, the service provides access to samples of the underlying feedback data that can be used to verify the numbers.

LMArena disclosed on occasion of the raise that AI Evaluations’ “annualized consumption run rate” has topped $30 million. The company will use the capital to cover the costs of operating its platform, finance AI research initiatives and hire more engineers.

Image: LMArena