Enable Overwrite existing alt text in the New Task filters to replace current strings; leave it off to fill missing only.
In Configure Product Settings, turn on Overwrite existing alt text when you want AI (and your format) to replace what is already there.
Leave overwrite off to only fill blanks. The Shopify admin product action “ALTSEO – Update Alt Text” always fills missing only and never overwrites.
Related help article: Read the guide →