Castor Labs releases UI performance profiler and bags $10M to refine developer UX

Tech · 4 min read

Castor Labs released a profiling tool that links runtime performance data—frame drops, paint times, layout thrash—to specific components and design tokens. The tool integrates with web and mobile stacks and visualizes hotspots in a way intended for both designers and engineers to act on.

The founders emphasize collaboration: product designers can see which interactions trigger jank and propose fixes, while engineers get actionable change lists. Castor also launched a plugin for design systems that surfaces performance cost estimates when designers choose complex components.

The startup raised $10 million to expand language support, add CI hooks for regression detection, and build integrations with major observability platforms. Early users report faster cross-team triage and fewer performance regressions shipping to production.