The Sentry JavaScript SDK has made significant efforts to reduce its bundle size by up to 35% through various optimization techniques. The company updated the underlying rrweb package from version 1 to version 2, which brought improvements but also increased the bundle size. To mitigate this, they implemented several strategies, including making build-time flags for tree shaking more accessible, removing unused code and features, such as canvas recording support by default, and updating the compression library to a smaller footprint. Additionally, they made it possible for users to host their own compression worker, reducing the bundled size by 10KB. These efforts resulted in a notable reduction in bundle size while maintaining functionality.