Beyond page content.
WHAT NEEDS ATTENTION
Menu items Button text Form labels and validation messages Search placeholders Date formats Email notifications Checkout steps, for shops Error pages Cookie and consent notices
WHY THIS MATTERS
Translated pages with English buttons looks unfinished.
A customer reaching an English checkout after browsing in their language frequently leaves.
WHERE THIS TEXT LIVES
In your theme and plugins, as interface strings.
Multilingual plugins provide a way to translate them.
WHAT TENDS TO BE MISSED
Email notifications Validation messages that only appear on error Anything in a plugin
HOW TO FIND THEM
Use the site in each language and look for untranslated text.
Deliberately trigger errors and check the messages.
FOR SHOPS
Complete a purchase in each language.
Check every email that sends.
WHAT TO KEEP A LIST OF
Strings you find untranslated, so you can address them systematically.