The best SEO APIs are Serphouse, Zenserp, Google Search API, DataForSEO, GeoRanker API, Keyword Suggestion API, SEO Extraction API, AuthoritasSERPs API, Serpstat API, and Article Rewriter API. These APIs provide various functionalities such as scraping SERP results in real-time, monitoring keyword ranking, structured SERP data, rank tracking, keyword generation for search engine marketing and SEO, SEO tags extraction from webpages, assessing keyword ranking, PPC data performance, and competitive research. The pricing of these APIs varies depending on the number of requests and features needed, with some offering free trials or plans starting at $1-10 per month.