Emil Kowalski

Emil Kowalski worked on the design team at VercelVercelVercel is a cloud application development and deployment company founded by Guillermo Rauch in 2015 as ZEIT. It contributes to the open-source React framework Next.js and provides application hosting, deployment and runtime services; its products later expanded to AI SDK, v0 and infrastructure for AI applications. The company adopted its current name in 2020 and raised a $300 million Series F in 2025.Open the full entry, where he developed the company’s design system, dashboard and other products.⁠[1]

He then worked at Linear as a design engineer. He has said that at Linear and Vercel he helped build the visual side of the product and marketing surfaces. As of November 2026, his website said he was taking a break from work.⁠[1][2]

In 2023 Kowalski built Sonner, a toast component library for React. He named it after a French word meaning “to ring,” which he considered more elegant than a name based on function, and he attributes its quick adoption mainly to its stacking animation, which had rarely been open sourced before. In his article on the project he wrote that Sonner is downloaded more than 40 million times a week from npm and used by companies including CursorCursorCursor is the trading name of U.S. AI coding software company Anysphere, Inc. and its namesake coding tool. Founded by Michael Truell, Sualeh Asif, Arvid Lunnemark and Aman Sanger, it began as an AI-native development environment forked from VS Code and later shifted toward agent-centered coding. Its November 2025 Series D valued the company at $29.3 billion post-money; on August 14, 2026, SpaceX completed an all-stock acquisition at an implied equity value of $60 billion, making Cursor a wholly owned subsidiary.Open the full entry, X and OpenAIOpenAIOpenAI is an artificial intelligence research and product organization founded in 2015 that develops the GPT model series, ChatGPT, Codex and a developer API, and conducts research on image, speech, video and intelligent agents. After its 2025 restructuring, the nonprofit OpenAI Foundation continues to control the for-profit OpenAI Group PBC. Its growth has involved large-scale fundraising and compute partnerships, and has also been accompanied by controversies over governance, copyright, privacy and AI safety.Open the full entry.⁠[3]

Vaul is a drawer component for React that he built, inspired by AppleAppleApple is a public technology company founded in 1976 and headquartered in Cupertino, California, United States. Its business includes the iPhone, Mac, iPad, wearables, and services such as digital content, payments, and cloud storage. The company builds its product system through in-house hardware, operating systems, and services.Open the full entry’s Sheet component on iOS. At Vercel the existing drawer component lacked drag-to-dismiss and had issues with inputs, so he built a new one from scratch and open sourced it. Vaul is built on Radix’s Dialog primitive and has an API similar to Radix’s.⁠[4]

As of November 2026, the Sonner and Vaul repositories on GitHub had about 13,100 and 8,600 stars respectively.⁠[5]

Kowalski teaches animations.dev, a course on web animation covering how to choose easing and timing, spring animations, and coding performant animations with CSS animations and Framer Motion. The course page says more than 13,000 designers and engineers have taken it.⁠[1]

His second course, AI for Designers and Engineers (aiforui.dev), teaches how to turn one’s design taste into rules and skill files that steer AI when building interfaces, and how to review AI output; it includes the 28 skills he uses every day and Lapse, a tool he built for reviewing animations. The course page says more than 4,500 designers and engineers have taken it.⁠[6]

Kowalski advocates writing a skill file for each aspect of an interface, turning the reasons why something feels better into rules for coding agents. “If you know what great feels like, describe the rules, then give them to your agents so they can follow them,” he wrote.⁠[7]

His GitHub repository skills (“Skills for Designers and Engineers”) had about 47,300 stars as of November 2026.⁠[5]

Personal website: https://emilkowal.ski/ (opens in a new window).⁠[2]

X: Public account: https://x.com/emilkowalski (opens in a new window).⁠[2][5]