sveltekit-data-flow

To manage SvelteKit data flow, place server-only logic in +page.server.ts and universal client-side logic in +page.ts. This separation ensures safe data serialization and deterministic patterns across server and client boundaries.

The best way to handle SvelteKit form actions is using preset patterns with fail(), redirect(), or error() as appropriate. These functions provide deterministic error handling and safe data serialization within your form submission workflows.

SvelteKit invalidation strategies automatically refresh data from load functions when underlying dependencies change. This ensures server and client data flow remains synchronized without requiring manual page reloads or complex state management.

SvelteKit server load data requires safe data serialization, meaning only JSON-serializable values can be returned from +page.server.ts. Following these serialization rules prevents boundary errors when passing data to the client.

You need universal load functions in +page.ts when data fetching logic must run on both server and client, whereas server-only loads in +page.server.ts are for sensitive data requiring deterministic patterns and safe data serialization.

SvelteKit form actions fail to return complex objects due to serialization rules requiring safe data serialization. You must return JSON-serializable data using fail() or error() to ensure successful client-side data flow.