Keyword clustering is the practice of deciding which search queries deserve one shared page and which need pages of their own. That framing matters: the goal is not sorting keywords into tidy folders, it is settling a page-count question before you write anything.
Take a store selling home fitness equipment. Searches for "adjustable dumbbells", "adjustable dumbbell set", and "dumbbells with adjustable weight" are three phrasings of one buying decision — a single page can rank for all of them. But "dumbbells vs kettlebells" is a different job entirely: that searcher has not picked a category yet, and a product listing will not answer them.
Getting the grouping wrong costs you in both directions. Split one topic across three pages and each version ends up thin, competing against its own siblings. Cram genuinely different intents onto one page and it answers nobody well enough to rank. Clustering replaces gut feel with two measurable signals — semantic similarity and SERP overlap — and this guide walks through both, then covers what to do with the clusters once you have them.