Chase Wiseman

Whatever your reasons, you may need your site’s visitors to confirm their age before viewing the content of your site. Age Verify does just that. It’s a simple plugin that lets you specify a minimum age and add an age-gate between a potential visitor and your content, just to be safe. Enjoy!

Age Verify

Like my review on another similar plugin, because this plugin uses PHP to check cookies, it doesn't work with cached pages...such as with the W3 Total Cache plugin or WP Engine.

Would be better with Javascript

A simple way to ask visitors for their age before viewing your content.

passbyme

PassBy[ME] use two-factor authentication with the highest known security standard, which is PKI. Rather than relying on a password authentication, which can be phished or guessed, PassBy[ME] second factor service adds a second layer of security to your WordPress accounts. It protects your website from hacks and unauthorized login attempts.
PassBy[ME] is easy to setup and use. You do not need software installation, just sign up for PassBy[ME] service and install the plugin.
Protect your WordPress website with PassBy[ME] The next generation authentication solution.

PassBy[ME] Two-Factor Authentication

PassBy[ME] improves the security of your WordPress website. Enable two-factor authentication for your users now.

Age Verify vs PassBy[ME] Two-Factor Authentication