Certainly! Here is a list of 41 highly recommended, 100% free SEO tools, organized in alphabetical order:

1. Ahrefs Backlink Checker: Analyzes backlinks and provides detailed information about them.
2. Answer the Public: Generates a list of questions people ask related to a specific keyword.
3. Bing Webmaster Tools: Offers insights into how your website performs on Bing search engine.
4. BuzzSumo: Helps you find popular content and analyze its performance.
5. Copyscape: Checks for duplicate content across the web.
6. Dareboost: Analyzes website performance and provides optimization suggestions.
7. Google Analytics: Tracks website traffic, user behavior, and more.
8. Google PageSpeed Insights: Measures website speed and offers suggestions for improvement.
9. Google Search Console: Monitors your website's presence in Google search results and provides valuable data.
10. Google Trends: Shows the popularity and interest over time for specific keywords.
11. GTmetrix: Evaluates website speed and suggests optimization strategies.
12. Hunter: Finds email addresses associated with a domain or company.
13. Keyword Planner: Helps identify keywords and provides search volume data.
14. Keywords Everywhere: Displays search volume, CPC, and competition data for keywords directly in your browser.
15. MozBar: Provides SEO metrics while browsing websites.
16. Moz Link Explorer: Analyzes backlinks and domain authority.
17. Neil Patel SEO Analyzer: Provides an overview of your website's SEO performance.
18. Ninja Outreach Lite: Helps find influencers and bloggers in your niche.
19. Open Site Explorer: Analyzes backlinks, domain authority, and anchor text.
20. Pingdom: Tests website speed and uptime, providing performance insights.
21. QuickSprout Website Analyzer: Offers a comprehensive analysis of your website's SEO.
22. Rank Math WordPress Plugin: An all-in-one SEO plugin for WordPress websites.
23. Screaming Frog SEO Spider: Crawls websites to analyze on-page SEO elements.
24. SEO Minion: Assists with on-page SEO tasks such as checking headers, alt tags, and broken links.
25. SEO Quake: Provides a detailed analysis of search engine results pages (SERPs).
26. SEO Site Checkup: Analyzes on-page and off-page SEO factors.
27. SEO Spider by Small SEO Tools: Crawls websites and provides insights on SEO issues.
28. SEOquake: Offers an SEO toolbar with various metrics and data points.
29. SERP Robot: Tracks keyword rankings on Google search results pages.
30. SimilarWeb: Analyzes website traffic, user engagement, and competitor data.
31. Siteliner: Scans websites for duplicate content and broken links.
32. Ubersuggest: Generates keyword ideas and provides search volume data.
33. Varvy SEO Tool: Evaluates on-page SEO factors and provides actionable recommendations.
34. Wayback Machine: Allows you to view historical snapshots of websites.
35. Web Developer Toolbar: Assists with various web development and SEO tasks.
36. WebFX SEO Checker: Analyzes website SEO performance and suggests improvements.
37. Yoast SEO: A popular WordPress plugin that optimizes on-page SEO.

Please note that while these tools are recommended by professional SEOs, it's always a good idea to assess their suitability for your specific needs and consult multiple sources before making a final decision.