MacSteini

Many users still browse with outdated browsers, often unaware of the risks. Upgrading ensures better security and reliability. This plugin displays a subtle notification prompting visitors to update their browser. Activate the plugin, and it works seamlessly.
Visit <a href="https://browserupdate.org/" rel="nofollow ugc">browserupdate.org</a> for more details.
Want to help translate this plugin? Visit the <a href="https://translate.wordpress.org/projects/wp-plugins/wp-browser-update" rel="nofollow ugc">WordPress Translation Project</a>.
<h3>Important Notice</h3>
Breaking Changes in Version 5.0 
– Requires PHP 7.4 or newer. 
– Ensure your hosting is updated to PHP 7.4 before upgrading to version 5.0 or newer. 
– Servers running older PHP versions are no longer supported. 
 – If your server is running an earlier PHP version, please download <a href="https://downloads.wordpress.org/plugin/wp-browser-update.4.8.1.zip" title="Download WP BrowserUpdate from WordPress.org" rel="nofollow ugc">version 4.8.1</a>.

WP BrowserUpdate

Used for a client who had this exact request. Worked well.

Works as expected

This plugin notifies website visitors to update their outdated browser in a non-intrusive way.

Deblyn Prado

So, you’re tired of people visiting your modern website with an outdated browser and not doing anything about it. Maybe they aren’t “power” users, maybe it’s your auntie running a last century browser trying to see awesome CSS3 animations and transforms. Let the user know that’s an outdated browser, and advise them on a better one.
With this solution you can check if the user’s browser can handle your website. If not, it will show a cool looking notice advising the user to update the browser. It\’ll be up to him/her to decide if he upgrades or not. Don’t force the user!
This plugin is a version of <a href="http://outdatedbrowser.com/" rel="nofollow ugc">Outdated Browser Projetct</a> created by <a href="https://github.com/burocratik" rel="nofollow ugc">Bürocratik</a>

WP Outdated Browser

Show a message if the user using a outdated browser.

WP BrowserUpdate vs WP Outdated Browser