ThemeGrill

Allows you to quickly create a maintenance/coming-soon page. You can use this plugin whenever your site is down for maintenance, currently going any upgrade or is in development. Built in options panel to add logo, background image, social icons, color, subscribe field and many more.
Get free support at http://themegrill.com/support-forum/
check the demo at http://themegrill.com/plugins/maintenance-page/
<h3>Features And Options:</h3>
<ul>
<li>Responsive design looks great on your devices.</li>
<li>Logo Upload</li>
<li>Background image/color option</li>
<li>Subscriber Feature to collect emails</li>
<li>Download subscriber list as csv</li>
<li>Social icons</li>
<li>Font Color option</li>
<li>Add title, text message option</li>
<li>Option to exclude page</li>
<li>Custom CSS</li>
</ul>
<h3>Maintenance Page Pro:</h3>
<ul>
<li>Counter</li>
<li>Contact Form</li>
<li>MailChimp integration</li>
<li>Ip Whitelist</li>
<li>Background Slider</li>
<li>Background Video</li>
<li>Progress Bar</li>
<li>Google font option</li>
<li>Analytic Code Option</li>
<li>Role Based access</li>
<li>Font size option</li>
<li>About Page</li>
</ul>
<a href="http://themegrill.com/plugins/maintenance-page-pro/" rel="nofollow ugc">Upgrade to Maintenance Page Pro »</a>
<a href="http://demo.themegrill.com/maintenance-page-pro/" rel="nofollow ugc">View Maintenance Page Pro »</a>

Maintenance Page

Allows you to quickly create a maintenance/coming-soon page. Use this plugin whenever your site is down for maintenance or undergoing development.

Harish Chouhan

Themeist Co

Build Mode lets you put your WordPress site into maintenance mode or display a coming‑soon page / under‑construction page with one click. Instead of a generic message, you can select and display any page you’ve built — with the Block Editor, Classic Editor, or a page builder. Visitors will see your chosen maintenance or coming‑soon page, styled using your theme’s CSS and JS, while logged‑in administrators continue working behind the scenes.
When Build Mode is active, only the content area of your chosen maintenance page is displayed. The header, footer and navigation are automatically removed.
<h3>Features</h3>
<ul>
<li>Enable or disable Build Mode from the Admin Bar</li>
<li>Choose any page as your custom maintenance, coming‑soon or under‑construction screen</li>
<li>Logged‑in admins bypass maintenance mode automatically</li>
<li>Sends correct 503 and Retry‑After headers (SEO‑friendly)</li>
<li>Lightweight and secure, built with WordPress best practices</li>
<li>Compatible with classic and block themes</li>
<li>Translation‑ready</li>
</ul>
<h3>Use cases</h3>
<ul>
<li>Show a custom under‑maintenance or coming‑soon screen while you redesign or update your site</li>
<li>Let search engines know your downtime is temporary with proper HTTP headers</li>
<li>Keep working on your site privately without showing a broken layout to visitors</li>
</ul>
<a href="https://themeist.com/plugins/build-mode/" rel="nofollow ugc">Plugin Page on Themeist</a> 
<a href="https://github.com/webtions/build-mode" rel="nofollow ugc">GitHub Repo</a>

Build Mode – Maintenance Mode & Coming Soon Page

Maintenance Mode & Coming Soon Made Easy – Display any page as your maintenance or coming-soon screen, no coding required.

Maintenance Page vs Build Mode – Maintenance Mode & Coming Soon Page