Workers compatibility dates of 2026-11-17 or later enable the new JavaScript module registry

Before updating, check your dependencies for invalid import attributes and changes to require() behavior. The new registry rejects invalid import attributes. Calls to require() also fail if the module or any of its dependencies use top-level await. To keep the legacy registry

Starting November 17, 2026, JavaScript Workers with a compatibility date of 2026-11-17 or later will use the new module registry by default. You will no longer need the new_module_registry flag for these dates. Python Workers keep using the legacy registry.