Phishing relies on a simple trick: a link's visible text says one thing (paypal․com) while its real destination points somewhere else
(paypal․account-verify․example), or hides behind a tracker or redirector that says nothing about where you will end up.

Reveal URLs shows you the URL each link in your mail points to and flags the ones where the visible text disagrees with it.

In Gmail, the add-on shows a card of findings for the message you have open.

- Suspicious links are flagged clearly; honest links are still shown without a warning.
- In the add-on's settings, you can ignore selected hosts and turn mismatch  highlighting on or off.
- Because Gmail add-ons run on Google's own servers, the open message is read and analysed there (by Google, who already hold your mail), never by us and never by anyone else.
- The add-on only reveals and flags links; it never changes, blocks or rewrites where a link points.

Also see: Email link phishing: your app should always show the URL:
https://www.phpfreelance.co.uk/blog/email-link-phishing-your-app-should-always-show-the-url