Every WordPress site needs this plugin.

The critical mass behind the Yoast SEO plugin makes any additional reviews completely unnecessary. But on the (very) off chance you’re still on the fence allow me to add my $0.02 of assurance that you need this plugin. Even if all you do is install and enable this plugin it will make your site better. Of course it has countless tools, settings, and options to make your site as search engine friendly as it can be. But my favorite feature is something that can easily go overlooked in SEO, the readability rating. An SEO genius I know always says that the best optimized search engine content is user friendly content. Having the ability to see the breakdown of how your content scores on readability, and how to improve it, not only makes you a better writer, but makes your site better optimized. No WordPress site should be without this plugin.