IDF

IDF stands for Inverse Document Frequency, a concept from information retrieval. It weights terms according to the number of documents in a defined collection that contain them. Very common words typically receive lower weight, while rarer and potentially more distinctive terms receive higher weight. The result always depends on the chosen document collection.

IDF is part of classic TF-IDF and related models. SEO tools may use their own comparison corpora, whose composition and freshness affect results. An IDF value does not fully represent search intent or content quality and is not a confirmed direct Google ranking factor.

• Measures rarity across a defined document collection
• Value depends on the comparison corpus
• Part of classic information-retrieval models
• Can support topic comparison
• Not a confirmed direct Google ranking factor