Siteimprove

The Siteimprove CMS Plugin bridges the gap between the WordPress content management system (CMS) and the Siteimprove Intelligence Platform. Now you can scan your website for errors as soon as a page is published, allowing you to fix mistakes, optimize content, and manage your site more efficiently. 
The plugin also provides you access to Prepublish, an add-on which allows you to check your page for issues before it has been published.

Turn your most complex website challenges into manageable tasks—all from a single platform

Matthew Muro

TinyMCE Spellcheck adds the spellcheck button back to the editor in WordPress 3.6 and up. This is a fork of the After the Deadline plugin which is now a part of Jetpack.

TinyMCE Spellcheck

TinyMCE Spellcheck adds the spellcheck button back to the editor in WordPress 3.6 and up.

Siteimprove vs TinyMCE Spellcheck