As stated in the Vue documentation: https://vuejs.org/api/compile-time-flags#webpack

__VUE_PROD_HYDRATION_MISMATCH_DETAILS__ should be set to false by default, otherwise, this warning pops up:

Feature flag VUE_PROD_HYDRATION_MISMATCH_DETAILS is not explicitly defined. You are running the esm-bundler build of Vue, which expects these compile-time feature flags to be globally injected via the bundler config in order to get better tree-shaking in the production bundle.