What is duplicate content, and is it penalized?

The same or nearly the same content appearing at more than one web address is called duplicate content, and in most cases Google doesn’t penalize it. Google treats it as a filtering matter. It groups the copies, picks one version to show, and leaves the others out of the results. The exception is copying done to manipulate rankings, such as republishing pages taken from other sites, which falls under Google’s spam policies.

Where duplicates come from

Mostly from accidents in how a site is set up, not from anyone copying anything. The usual sources on a home-service site:

• One page reachable at several addresses: with and without www, on http and https, or with tracking codes added to the end.
• A test copy or an old version of the site left open to search engines.
• The same service description pasted onto every city page with the city name swapped.
• Manufacturer text used as supplied, which also appears on every other dealer’s site.
• Another site copying your text.

What Google does with duplicates

It picks one. Google calls the version it chooses the canonical, meaning the one it treats as the main copy. The others are still known to Google but are usually not shown. Google says it tries to combine the signals from the copies, such as links, onto the version it picks.

So there’s no penalty, but there’s a cost. Google may pick a version you wouldn’t have chosen, such as an address with a tracking code on the end. A visitor may land on a copy that is out of date. And if your Carlsbad page and your Oceanside page are the same apart from the name, Google may show only one of them, which defeats the purpose of having both.

When it does break Google’s rules

The purpose has to be manipulation. Google’s spam policies cover scraped content, which is content taken from other sites and republished with little or nothing added. They also cover doorway pages: many near-identical pages, each aimed at a slightly different search, that all lead to the same place. Rows of city pages with one word changed sit close to that line, close enough to raise the question of whether city pages count as doorway pages.

If Google’s reviewers took action against a site for this, a notice would appear in the Manual actions report in Google Search Console. An empty report means no manual action is in place.

How to check and fix it

Check with Google’s own tool first. The URL Inspection tool in Search Console reports which address Google has selected as the canonical for a page, and whether that matches the one your site declares. (A URL is the web address of a page.) Where they differ, or where copies exist, the fixes are these:

• Redirect every variant of an address permanently to one version.
• Where a page must exist at more than one address, add a canonical tag naming the main one.
• Close test copies of the site to search engines, or remove them.
• Rewrite city pages so each says something true only of that place.
• Write your own descriptions in place of manufacturer text.

The first three are technical work that I handle under indexing and crawling. The last two are writing. If another site has copied you, Google usually works out which is the original, and there’s a legal removal process for copyright complaints. Check Google’s current instructions before using it, because I’m not giving legal advice here.

Is it the same as keyword cannibalization?

No. Duplicate content is one piece of text at several addresses. Keyword cannibalization is several different pages aimed at one search. A site can have either without the other.