WordPress plugin
Maintenance Page Pro for WordPress Maintenance Pages
Maintenance Page Pro extends Maintenance Page for WordPress sites undergoing an upgrade, in development, or temporarily unavailable. It adds settings for the page visitors see while work is underway.

Maintenance Page Pro extends Maintenance Page for WordPress sites undergoing an upgrade, in development, or temporarily unavailable. It adds settings for the page visitors see while work is underway.
Build the visitor page
The base add-on offers a responsive maintenance or coming-soon layout. Add a logo, background picture or color, title, message, social icons, and font color. It also includes a subscriber field, custom CSS, and page exclusions; collected subscriber emails can be downloaded as a CSV file.
Choose content and appearance options
Pro options include a counter, contact form, and progress bar. The subscriber feature can connect to MailChimp. For the page styling, use a background image slider or video, use the Google font option, and adjust font size. You can also add analytic code or an About Page.
Manage access and activate
The IP Whitelist allows specified IP addresses, while role-based access manages access according to visitor roles. To activate the page, install and activate Maintenance Page, open Settings > Maintenance Page > General, and check Activate the Maintenance Page. Configure the branding, background, message, social icons, subscriber field, and any Pro settings needed.
If changes are not visible, check in another browser while logged out. When caching extensions are present, purge the cache or temporarily deactivate caching while testing activation and design changes.
The current listing says Maintenance Page has not been tested with the latest three major WordPress releases, so compatibility and support on newer releases may be uncertain.