There are many free resources available online for learning about SEO and optimizing your website for search engines. Here are some of the best ones:

Moz: Moz offers a variety of free SEO tools and resources, including a beginner's guide to SEO, a keyword research tool, and a link explorer.

Google Search Console: Google's free tool for webmasters provides insights into how Google crawls and indexes your website. It also provides data on search queries, clicks, and impressions.

SEMrush: SEMrush offers a free version of its toolset, which includes keyword research, site audit, and backlink analysis.

Ahrefs: Ahrefs offers a free version of its toolset, which includes a backlink checker and site explorer.

Yoast SEO: Yoast SEO is a popular WordPress plugin that helps with on-page optimization. They also offer a free SEO for beginners course.

Search Engine Land: Search Engine Land is a leading source for news and information about search engine marketing. They offer many free resources, including guides and tutorials.

Backlinko: Backlinko is a popular SEO blog that provides in-depth guides and case studies on various SEO topics.

Neil Patel: Neil Patel is a well-known digital marketer who offers a wealth of free SEO resources on his website, including blog posts, videos, and courses.

HubSpot: HubSpot offers a variety of free SEO tools, including a website grader, keyword research tool, and content strategy tool.

Google Analytics: While not specifically an SEO tool, Google Analytics provides valuable data on your website's traffic and performance, which can help inform your SEO strategy.