All modern web applications should be using UTF-8 encoding. For developers with English keyboards (where all keys produce 7-bit ASCII), testing web forms with multibyte characters can be a pain. You can, of course, enter Unicode characters via obscure key combinations, but using this bookmarklet may be easier:
This simply visits all text/password/textarea inputs on a page and replaces Latin vowels with multibyte variants. E.g. John A Public ⇒ Jōhn Ā Pūblīc.
Test it here
The bookmarklet prompts me for “Match beginning”. What is this?
If you only want to affect certain inputs, enter a phrase at the prompt. The bookmarklet will then only affect inputs whose values start with that phrase. E.g. To affect only a “comment” field, place “||” at the beginning of the field, and enter “||” at the match prompt. The bookmarklet will affect only this field and strip the “||” from the field for you.