Keyword Cannibalization
Keyword cannibalisation happens when two or more pages on your own site compete for the same query. Search engines struggle to choose between them, so signals split and neither page ranks as well as one consolidated page would have done.
Why it matters for your rankings
Cannibalisation is usually caused by success rather than carelessness. A team publishes consistently for years, and eventually four articles overlap on the same subject because nobody audited what already existed.
The damage is subtle enough to go unnoticed. Rankings do not collapse, they simply stall at positions five to eight while a competitor with one authoritative page occupies the top. Backlinks split across your versions, internal links point in different directions, and Google swaps which URL it shows week to week, which is itself the clearest diagnostic. The fix is almost always consolidation into a single stronger page, not further optimisation of the competing ones.
How to check it on your site
Look for URL swapping
In Search Console, filter Performance by query and add the Pages dimension. Multiple URLs alternating for one query is cannibalisation.
Run a site search
Search site:yourdomain.com plus the target phrase. If several pages look like they answer the same question, they probably do.
Decide on one winner
Pick the page with the strongest links and best performance. Merge the useful content from the others into it.
Redirect and re-link
301 the losing URLs to the winner and update internal links so they all point at the consolidated page.