I have the following set of NSExtensionActivationRule. My extension displays in Safari, Firefox, and Chrome.
<key>NSExtensionActivationRule</key> <string>SUBQUERY ( extensionItems, $extensionItem, SUBQUERY ( $extensionItem.attachments, $attachment, ( ANY $attachment.registeredTypeIdentifiers UTI-CONFORMS-TO "public.url" || ANY $attachment.registeredTypeIdentifiers UTI-CONFORMS-TO "public.plain-text" ) ) .@count == $extensionItem.attachments.@count ) .@count == 1</string>
ThE uSeFuL
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