Understanding it
The problem is not having 2 pages that contain the same word. It is having 2 pages that answer the same question. “Website redesign cost” and “website redesign timeline” can coexist. Two articles on “how much does a website redesign cost” compete with each other.
The most common sign shows up in Search Console: for the same query, the URL that appears changes from week to week, and the ranking stays unstable. Links can cause it too: if many “SEO agency Lyon” anchors point to the homepage, it competes with the dedicated page.
It typically affects sites that publish a lot without an overall plan, stores whose filters generate thousands of near-identical pages, and redesigned sites that keep both the old and new version of a page.
A concrete example
Illustrative example: three articles for one question
Over 4 years, a law firm has published 3 articles on “mutual termination of an employment contract”: a guide, a regulatory update and an FAQ. None gets past page 2, and Google rotates between the three.
The firm merges them into one complete, up-to-date guide, 301-redirects the 2 old URLs to it and updates its internal links. A single page now carries the topic, with the combined links and history of all three.
The common mistake
Deleting a page without a redirect
Removing the “extra” page loses its links and leaves visitors on a 404 error. Merge the useful content into the page you keep, then 301-redirect the old URL to it. If the two pages actually answer different intents, differentiate them instead of merging.