What it does: Every marketer needs to understand SEO. Ahrefs makes this job simple and straightforward. You can track keyword performance, measure your social metrics, perform backlink analysis, analyze your content, explore trending content, measure your keyword positions and do keyword research. It’s a robust all-in-one SEO tool that will put you on the path to outrank your competitors. How much it costs: Plans range from $79 to $2,500 per month. Why it’s worth it: There are plenty of free SEO tools, but few of them provide the full breadth of reliable information that Ahrefs does. Ahrefs’s quality data and reliable results are an essential part of dominating SEO.