The 20 hottest open source startups of 2025

The 20 hottest open source startups of 2025

A recent report spotlighting the world’s top 20 trending open source startups reveals that more than half of these innovative companies have a strong AI focus. This evaluation underscores the growing global appetite for projects that blend open source startups principles with cutting-edge artificial intelligence.

The report is the work of European venture capital firm Runa Capital, which has been curating the ROSS Index since 2020. The Index tracks the fastest-growing vendor-led open source startups by looking at GitHub “stars” – a social media-like indicator of popularity. In 2023, Runa Capital expanded its approach by releasing annual reports that highlight the most sought-after commercial open source startups.

Last year, the report showed that AI and data infrastructure were key growth drivers for open source startups, with LangChain topping the list for its framework centered on large language models. This year, the trend continues with AI at the heart of 11 out of the top 20 open source startups.

It is also important to note that the ROSS Index is carefully curated. Only projects with a close tie to a commercial company qualify – side projects are left out. In addition, to be listed, these open source startups must be less than 10 years old, have raised under $100 million in funding, and maintain full independence as neither a subsidiary nor a publicly traded entity.

The 20 hottest open source startups of 2025

Leading the 2024 ROSS Index is Ollama, a Y Combinator alum known for its open source tool that enables local operation of LLMs like Meta’s Llama and DeepSeek. With its GitHub star count skyrocketing by roughly 76,000 in 2024 – a 261% increase to over 105,000 stars (currently more than 135,000 stars) – Ollama stands as a prime example of the rapid growth of open source projects.

Next up is Zed Industries, which offers a cross-platform collaborative code editor built for seamless interaction between humans and AI. Although Zed has been around for a while, it only adopted an open source model in January 2024. Since then, its GitHub repository has attracted more than 52,000 stars.

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In third place, LangGenius is making waves with its LLM app development platform called Dify. The project experienced a remarkable boost – growing from around 13,000 to nearly 57,000 GitHub stars last year, and now has garnered more than 84,000 stars.

Following closely is ComfyUI, an intuitive node-based application that generates images, videos, and audio using generative AI models. The project’s star count on GitHub climbed by 195% to reach 61,900 stars over the past year.

Completing the top five is All Hands, the company known for its open source platform OpenHands for software development agents. Since its launch last March, OpenHands has earned 39,600 GitHub stars, with an additional 12,000 stars added later in the year.

While last year’s ROSS Index underscored the explosive growth of AI and LLMs, it also highlighted that developer tooling remains a vibrant area in open source. For example, projects like Zed and Astral’s UV (ranked No. 9) continue to resonate strongly with developers. Additionally, tools such as the PDF manipulation utility Stirling PDF (No. 7), finance management software Maybe Finance (No. 8), and remote desktop solution RustDesk (No. 17) demonstrate the ongoing demand for self-hostable, privacy-focused applications.

The inclusion of Ethereum blockchain-focused Fuel (No. 12) further confirms that crypto and web3 technologies continue to thrive.

Open source software has long been a collaborative effort that brings together contributors from around the world. Even vendor-led projects share this spirit by involving global communities, even if the company’s formal operations remain concentrated in a specific region.

The report reveals that six of the top 20 ROSS startups are based in San Francisco, while Canada hosts three. The remaining companies are spread across Europe (including the U.K., Switzerland, Hungary, and the Czech Republic), Singapore, and China.

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Methodology

There are several ways to monitor the buzz around “hot” open source projects. For example, Two Sigma Ventures curates its own
Open Source Index which, unlike the ROSS Index, features the top 100 projects irrespective of a commercial angle and offers diverse filtering options.

Additionally, GitHub itself maintains a
trending project list that showcases popular repositories without focusing on commercial startups.

It is also valuable to examine the
methodology behind the ROSS Index. While GitHub “stars” serve as an indicator of a project’s appeal, they simply reflect that users have given the project a “like” rather than actively engaging with it. Older projects naturally accumulate more stars, which is why Runa Capital emphasizes the relative growth over a 90-day period for quarterly updates, and the absolute number of new stars over the year for its annual report.

This approach sometimes results in the annual report differing from the quarterly reports since absolute star counts do not always mirror rapid, short-term growth patterns. Additionally, while many projects included have adopted recognized open source licenses, the ROSS Index focuses on the “commercial perception” of open source rather than a strict definition. For instance, even if a project uses the Server Side Public License (SSPL) – a license the Open Source Initiative has yet to endorse as open source – it still qualifies under Runa Capital’s criteria.

Overall, the ROSS Index offers a valuable insight not only into the trends in open source technology, but also into the companies striving to build successful businesses on these innovative tools.

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