SEO tools suggest content through four main data streams: search demand analysis, competitor gap identification, query expansion, and topical clustering. They pull keyword volume and difficulty metrics from databases built on Google Keyword Planner data, Clickstream data, and their own crawling. When you enter a seed topic or domain, the tool maps thousands of related queries people actually search for, then filters by volume, difficulty, and relevance. Competitor gap analysis is the most actionable method. Tools like Ahrefs, SEMrush, and Surfer SEO crawl your competitors' top pages, extract the keywords those pages rank for, then highlight terms where competitors rank in the top 10 but you don't appear at all. This creates an instant content opportunity list based on proven demand in your niche. At Ottawa SEO, we run gap reports against 3-5 direct competitors quarterly to find low-hanging fruit our 500+ domain portfolio hasn't captured yet. Query expansion pulls from Google's own suggestion engines: autocomplete predictions, People Also Ask boxes, and related searches at the bottom of SERPs. Tools scrape these in bulk and organize them into question-based content ideas, long-tail variations, and semantic clusters. This is why you'll see tools recommend "how to," "best," and "vs" style articles—they mirror what Google already shows users want. Topical clustering algorithms identify content gaps within your existing architecture. If you've published 20 articles about WordPress security but nothing about WordPress performance, the tool flags performance as an authority gap. It builds topic maps showing parent topics, subtopics, and supporting articles you need to establish topical depth. The suggestions are only as good as your filters. Raw output includes thousands of keywords, most irrelevant. We typically filter by search volume over 100/month in Canada, keyword difficulty under 40 for newer sites, and manual review for commercial intent. Tools don't understand your business model or audience nuance—they show demand, but you decide if that demand converts.