Reveal URLs is compatible with the Gmail™ email service.

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 names a URL or host that does not match it. It does
not follow redirects, so it shows the tracker or redirector URL, not where it lands.

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

- Suspicious links are flagged clearly; non-mismatching 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 the Gmail add-on runs on servers operated by Google LLC, the open
  message is read and analysed there (by Google LLC, 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

Gmail™ is a trademark of Google LLC.