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.
WP BrowserUpdate is based on the browser-update.org detection logic. The plugin now runs independently from browser-update.org at display time: the visitor-facing notification is served from the plugin’s own bundled runtime files, so sites do not need to load scripts, styles, or default notification links from browser-update.org. browser-update.org remains the credited upstream source for the bundled detection logic, and future runtime refreshes are tracked with source URLs and hashes in the plugin assets.
Visit <a href="https://browserupdate.org/" rel="nofollow ugc">browserupdate.org</a> for more details about the upstream project.
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>How it works</h3>
WP BrowserUpdate bundles browser-update.org detection logic for WordPress. After activation, the plugin loads the local notification runtime from the plugin directory and passes your configured browser-version thresholds to those scripts. The notification is shown only when the bundled detection logic matches a browser to your settings.
The settings page is available under Settings > WP BrowserUpdate. You can define browser versions for every browser key supported by the bundled browser-update.org runtime, choose where the message appears and which element should contain it, enable testing mode, decide whether mobile or unsupported browsers should be notified, customize links, language and message text, and add trusted custom CSS for the notification.
Browser version fields accept major versions such as <code>115</code> and positive dotted versions such as <code>137.0.3912.63</code>. Dotted versions are passed exactly to the bundled runtime instead of being reduced to their major version; exact comparison depends on the bundled browser-update.org logic and the browser key used by that runtime. A value of <code>0</code> uses the default bundled outdated-browser detection. Negative whole numbers are passed to the bundled runtime as relative offsets from the current bundled upstream version.
Microsoft Edge and Microsoft Internet Explorer have separate settings now.
This local runtime design avoids frontend blocking of external script URLs on sites with strict Content Security Policies or tracker blocking. WP BrowserUpdate ships only the local runtime and CSP adapter files needed by the plugin.
<h3>Important Notice</h3>
Breaking Changes in Version 6.0 
– Requires WordPress 6.0 or newer. 
– Introduces a new structured settings model to support the browser-update.org customization surface used by WP BrowserUpdate. 
– Moves the visitor-facing browser-update.org runtime into the plugin package so strict Content Security Policies and tracker blockers no longer need to allow scripts from <code>browser-update.org</code>. 
– Existing WP BrowserUpdate settings from version 5.x are migrated automatically.
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.

Geoffrey

This plugin adds a message before or after (or both) your post content when this post is outdated. 
You visitor knows when a post is a little bit outdated and reads the content keeping its age in mind.
Features
<ul>
<li>Choose the place where the message is displayed (before or after the content, or both)</li>
<li>Choose which type of posts that are concerned</li>
<li>Custom delay for each post</li>
<li>Hide the message for a specific post (directly from the edition page)</li>
<li>Shortcode and template function</li>
<li>Lots of hooks (for developers)</li>
</ul>
A full documentation is coming.
If you find a bug, please, <a href="https://wordpress.org/support/plugin/juiz-outdated-post-message" rel="ugc">tell me</a>!
You want to translate this plugin and have your name in this page? Find translation files <a href="https://plugins.svn.wordpress.org/juiz-outdated-post-message/trunk/languages/" rel="nofollow ugc">here</a>.

Juiz Outdated Post Message

Simple to integrate, best practice for bloggers ! This plugin is on my toplist ! :)



Nice feature and easy to use

I've already said that to a lot of people, this one is a MUST HAVE.



great idea, UX topissimo

Works like a charm! 

If you want to use the shortcode in your template, do it like this : 
<?php echo do_shortcode('[outdated]'); ?>

Works with WP 4.7.x

This plugin adds a message before or after your post content when this post is outdated

WP BrowserUpdate vs Juiz Outdated Post Message