How to handle browser storage in Angular SSR?

When using Angular SSR, browser APIs like localStorage are unavailable on the server, causing build errors. The solution involves creating a BrowserStorageService using an InjectionToken wrapping localStorage for the browser, then creating a BrowserStorageServerService that extends it with a mock Storage implementation for the server. The server-side config uses Angular's ClassProvider (provide/useClass) to substitute the server implementation automatically, allowing the app to run on both platforms without errors.