What is Topic cluster?
A topic cluster is a group of related pages built around one broad "pillar" page, all interlinked, which signals to search engines that a site covers a subject in depth rather than mentioning it once.
Also called: content hub, pillar page, hub and spoke content.
Search engines no longer rank isolated pages against keywords; they assess how well a site covers a subject. A single 3,000-word article on boiler servicing is one signal. A pillar page on boiler servicing linked to twelve pages on noises, pressure loss, annual costs, landlord obligations and the rest is a body of evidence.
The internal links are the mechanism, not decoration. They pass authority inward to the pages you most want to rank, and they keep readers moving through your site instead of back to the results page. A cluster with no links between its pages is just a folder.
It is also the most reliable way to plan content without staring at a blank calendar: pick the five subjects your customers actually ask about, and each becomes a cluster with a year's worth of obvious pages inside it.
What to actually do about it
- Choose one broad pillar subject and give it a substantial page.
- List every real question inside that subject; each becomes a spoke page.
- Link every spoke to the pillar, and the pillar to every spoke.
- Link laterally between spokes wherever it genuinely helps the reader.
- Don't build two clusters that compete for the same phrase.
Koo maps your keywords into clusters, shows which spokes are missing, and wires the internal links between pillar and spokes automatically as new pages publish.
Related terms
Long-tail keyword
A long-tail keyword is a longer, more specific search phrase with lower search volume but clearer intent and far less competition — for example "repair a leaking radiator valve in Leeds" rather than "plumber".
Keyword difficulty
Keyword difficulty is an estimated score, usually 0–100, of how hard it would be to rank on the first page for a search phrase, based mainly on the authority and backlink profiles of the pages already ranking there.
Meta description
A meta description is a short summary in a page's HTML — best kept under about 155 characters — that search engines often display beneath the page title, acting as the advert for the click.