What does an SEO agency do?
An SEO agency improves how your site ranks in Google and other search engines. That work spans three layers: technical SEO (site speed, crawlability, indexation, structured data), on-page SEO (title tags, content targeting, internal linking), and off-page SEO (backlink acquisition, digital PR, authority building). Most US SEO agencies also handle content strategy and production. The strong ones start by auditing what's already broken; the weak ones sell "more content" as the answer to every problem.
Why this matters
This question shows up regularly in Google's People Also Ask for the "seo agency" query, which is a signal that buyers in this space are asking it constantly during their research phase. The answer above is written from The Wall's editorial position — we index 2,286 verified US growth-services vendors across 10 pillars and see how these questions map to actual buying decisions.
If you're evaluating vendors in this category, the SEO pillar page has the full US firm list with rates, team sizes, and headquarters filters.