It's not just Not Invented Here Syndrome. Some technologies like CSS simply don't scale if you're building some of the largest websites on the planet with thousands of engineers committing to the same code base every day. StyleX is Meta's open-source solution for CSS at scale and allows atomic styling of components while deduplicating definitions for bundle size and exposing a delightfully simple API for developers.

Tune in to learn from Melissa, one of the StyleX maintainers how Open Source has acted as a force multiplier for the project, how interacting with other large companies adopting StyleX has been, and much more!

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Links

• How AI Is Transforming the Adoption of Secure-by-Default Mobile Frameworks: https://engineering.fb.com/2025/12/15/android/how-ai-transforming-secure-by-default-mobile-frameworks-adoption/

• StyleX: https://stylexjs.com

• MTP 67: Measuring Developer Productivity with Diff Authoring Time: https://pca.st/pt4p4tv5

Timestamps

• Intro and news 0:06

• Introduction Melissa 1:47

• Why did we build our own styling system? 4:07

• StyleX API 5:36

• cx vs StyleX 7:37

• Component styling and priorities 10:38

• How StyleX evolved in the past seven years 15:20

• Community influence 19:33

• Open Source 24:07

• Challenges of OSS 27:02

• Managed breaking changes in OSS 29:48

• Measuring success for StyleX 32:04

• Packaging challenges 34:34

• StyleX competition 38:42

• Creating the StyleX roadmap 40:24

• Outro 43:15