Svelte 5 migration examples often look simple. Replace the old reactivity, switch the event syntax, move state into runes, and keep going.
A real application is less cooperative. State crosses component boundaries. Events connect code written at different times. Browser-only behavior gets mixed with server-side rendering. Something that looks like a harmless cleanup can break code that was working yesterday.
I recently published a practical guide covering ten migration traps that can cause those problems. It focuses on moving an existing application forward in controlled steps instead of trying to modernize everything at once.
The guide covers problems involving:
- shared state and derived values;
- component events and callback props;
- server-side rendering and browser-only APIs;
- legacy and migrated components running together; and
- tests that catch behavior changes before users do.
I also put together a tested GitHub example with legacy and migrated versions of the same small order calculator. The example gives you something concrete to compare, change, and test. That is usually more useful than another perfect code fragment that has never met a real application.
Read the guide and use the checklist
Read 10 Svelte 5 Migration Traps That Can Break a Real Application on Medium.
Work through the free 40-item Svelte 5 migration checklist.
View the tested migration example on GitHub.
What is causing trouble in your migration?
If you are working through a Svelte 5 migration, I would like to know where it is getting stuck. Which part has taken the most time? What failed after it appeared to work?
Leave a comment below or open an issue on GitHub. The answers will help me decide which migration problem to investigate next.