Slim SEO is an SEO plugin for WordPress, made by the Slim SEO team, whose other products include the Meta Box plugin. SEO (search engine optimization) means preparing pages so that search engines such as Google can understand and rank them. Slim SEO does most of this work automatically after installation, with very few settings.
It generates meta titles and descriptions, Open Graph and Twitter card tags (the preview data that social networks show for a shared link), schema markup (structured data that describes a page's content to search engines), an XML sitemap and breadcrumbs. It also adds missing image alt text, redirects old or broken URLs, monitors 404 errors, and inserts code such as Google Tag Manager into the page header or footer. Slim SEO Pro adds a visual schema builder with more than 30 schema types and custom JSON-LD, internal link reports and suggestions, broken-link repair, Google Search Console reports inside WordPress, and a writing assistant.
The base plugin is free and fully functional; it needs a self-hosted WordPress site. Slim SEO Pro is a yearly license priced by the number of websites.