Svelte 5: event handlers are case-sensitive

[kyoshino]

Describe the bug

In Svelte 5, event handlers like on:click are now onclick. However, onClick (capital C) doesn’t work even though it’s valid in HTML. I just realized it by accidentally writing onClick by myself.

Event handlers should be case-insensitive to avoid confusion.

Reproduction

REPL

Logs

No response

System Info

Svelte 5.0.0-next.246

Severity

annoyance

[brunnerh]

Duplicate of:

• [Svelte 5] Events should be allowed to be camelCased #10044

[kyoshino]

Closing this as unplanned is fine by me, but at least it should be documented.

[dummdidumm]

Documented here https://github.com/sveltejs/svelte/blob/main/documentation/docs/02-template-syntax/02-basic-markup.md#events, which will appear on the final site soon