What Are the Key Features to Include in a Free Audit SEO Tool?

Hello Dev Community,

I’m interested in developing a free audit SEO tool and would love some advice on essential features. What functionalities do you think are most valuable for users, such as keyword analysis, backlink checking, or on-page SEO suggestions? Also, are there any recommended tech stacks or libraries that could simplify development for this type of tool?

Thanks in advance for your insights!