🔑 Keyword Density Checker

🔍 See the most-used words and phrases on any page or text. Density is the percentage each term contributes to the total — useful for spotting keyword stuffing or for understanding what a page is really about. Bigrams and trigrams reveal the natural phrases your content emphasises.

Natural Language Processing in SEO: N-Grams, Lexical Diversity & Semantic Coverage

Early search algorithms relied heavily on exact-match word frequency. Modern search engines evaluate topical depth, entity co-occurrence, and semantic coherence using transformer models (such as BERT and MUM).

N-Gram Tokenization Explained

An n-gram is a contiguous sequence of n items from a given sample of text:

  • Unigram (1-word): security, certificates, encryption. Useful for broad vocabulary measurement.
  • Bigram (2-word phrases): ssl certificate, public key, cipher suite. Discovers compound subjects.
  • Trigram (3-word phrases): transport layer security, certificate authority authorization. Reveals precise technical entities and intent.

Lexical Diversity & Type-Token Ratio (TTR)

Lexical diversity measures the proportion of unique words relative to total words in a text corpus:

Lexical Diversity = (Unique Words / Total Words) × 100

High-quality technical documentation typically exhibits a balanced lexical diversity (30% to 55%). Content with very low diversity often suffers from repetitive phrasing, thin copy, or keyword stuffing.

Stopword Filtering

Stopwords (e.g. the, is, at, which, on) represent over 40% of standard English text. Removing stopwords allows analysis to isolate high-entropy content terms that represent the core subject matter.

Why Keyword Stuffing Triggers Algorithmic Penalties

Artificially inflating a target phrase beyond 2.5% to 3% of total content creates poor reading cadence and triggers spam filters under Google's Helpful Content System. Instead of repeating identical keywords:

  • Incorporate LSI (Latent Semantic Indexing) entities: Related subtopics, synonyms, and contextual terminology.
  • Structure your narrative around answering secondary search intents (how-to steps, troubleshooting, technical specifications).
  • Audit heading tags and overall content hierarchy using our On-Page SEO Checker.

Frequently Asked Questions

What is the ideal keyword density percentage?

There is no fixed mathematical target. Most naturally written, authoritative articles have a primary keyword density between 0.5% and 1.5%. If your primary bigram/trigram flows naturally in headings and introductions, density is sufficient.

How does TF-IDF differ from simple keyword density?

Keyword density only measures term frequency on one page. TF-IDF (Term Frequency-Inverse Document Frequency) compares term frequency against a broader library of documents, penalizing commonly occurring words while elevating rare, highly specific topical phrases.

How does word count relate to keyword density?

Shorter articles require fewer keyword repetitions to establish topical relevance. Check overall document length, syllable counts, and reading level with our Word Count & Readability Checker.