AI KEYWORD DENSITY
& NLP ANALYZER

Keyword density is the percentage of times a target keyword appears on a page relative to the total word count. For traditional Google SEO, a density between 1% and 2% has long been considered the sweet spot — high enough to signal topical relevance, but low enough to read naturally. Going far above that range historically triggered over-optimisation filters, while going too low left the page under-relevant for the target query.

AI search engines such as ChatGPT, Perplexity, and Google’s Gemini treat keyword density very differently. Large language models do not count exact-match occurrences the way a 2014-era crawler would. Instead, they build a semantic vector from the entire page — weighing synonyms, related entities, co-occurring terms, and structured data. A page that uses the primary keyword only 0.8% of the time but thoroughly covers related entities (e.g. “search intent”, “SERP features”, “canonicalisation”) will typically outrank a page stuffed with the same phrase at 4% density.

Keyword stuffing hurts. Google’s helpful content system and spam updates actively demote pages that repeat a keyword unnaturally. Symptoms include: the same phrase appearing in every heading, awkward grammar forced by the keyword, and densities above 3% for the primary term. Recovery from a stuffing-related penalty can take months and usually requires rewriting the content entirely — so it is far cheaper to write naturally the first time.

The ideal range for modern content is 0.5%–2% for the primary keyword and 0.5%–1% for each secondary keyword. Pair this with semantic entities (people, places, concepts, tools), clear heading hierarchy, and JSON-LD schema. This combination satisfies both the classic ranker and the retrieval-augmented generation pipelines that power AI Overviews and answer engines.

Topical depth beats keyword repetition. Modern AI engines — Google SGE / AI Overviews, ChatGPT with browsing, Perplexity, Gemini, and Claude — evaluate whether a page demonstrates comprehensive coverage of a topic, not whether a single phrase is repeated enough times. They do this by extracting entities, building a knowledge graph from the page, and comparing it against the expected entity set for the query. A page that mentions the primary keyword only 0.8% of the time but covers 8–10 related entities will typically outrank a page stuffed with the same phrase at 4% density. In practice this means: do not just repeat the keyword — prove you understand the topic by covering its subtopics, edge cases, and related concepts.

Concrete example. Instead of stuffing “best running shoes” 10 times across a 1,000-word page (a 3% density that reads as spam), mention it 8–10 times naturally and weave in related entities that AI engines expect to find on a comprehensive page: cushioning, arch support, pronation, trail vs road, drop height, breathability, durability, and weight. These terms signal to ChatGPT, Perplexity, and Google’s SGE that the page is an authoritative answer — not a thin affiliate post. When the user asks “what should I look for in running shoes?”, AI Overviews surface the page that mentions cushioning and pronation, not the page that repeats “best running shoes” twelve times.

Recommended density ranges at a glance:

• Primary keyword: 0.5%–2% of total word count (e.g. 5–20 mentions in a 1,000-word page).
• Secondary keywords (2–3 variations): 0.5%–1% each — long-tail variants, question forms, and branded terms.
• Related entities: 5–10 distinct entities mentioned at low density (1–3 mentions each) — enough to appear in the page’s semantic vector without dominating it.
• Stuffing threshold: anything above 3% for the primary keyword is a red flag for both Google’s helpful content system and AI retrieval pipelines.

This analyzer extracts every word-level signal above and compares your page against both benchmarks — the legacy density check and the modern semantic-relevance check. Use the Stuffing Risk score as your early-warning system, and the Missing NLP Entities list as your expansion roadmap for AI visibility.