How to Fix Duplicate Content
What this means
Two or more of your pages have almost the same text. It might be the same page at two addresses, two location pages with only the town name changed, or product pages with identical descriptions.
Google doesn't punish a site for this. But it shows only one page from a set of near-identical pages, and it might not pick the one you want.
Why it matters
Pages that compete with each other split the attention Google would give one clear page. The version that ranks may be an older page, one with a tracking code in the address, or one that doesn't convert as well. And visitors who find two copies of the same thing trust the site less.
How to fix it
Work out why the pages are similar first, because the fix depends on it.
The same page at two addresses
This happens with www and non-www versions, http and https, tracking codes, printer-friendly pages, or a product listed in two categories.
The fix is technical, not writing: keep one address, and either redirect the others to it or add a canonical tag on each copy pointing at the main one. The guides on redirects and canonical tags explain both. Shopify, Wix and Squarespace handle most of this for you.
Pages that cover the same topic
Two blog posts about the same question, or a service described on two pages.
Merge them into one better page. Keep the address that gets more visits (Google Search Console shows which), move the best parts of the other page into it, then redirect the other address. One thorough page beats two thin ones.
Pages that are meant to be different but read the same
Location pages and product variants are the usual case: "Plumber in Leeds" and "Plumber in York" with only the town swapped.
Rewrite each page so it's genuinely useful on its own. For location pages, add the areas you cover, local jobs you've done, travel times, local prices or reviews from that town. For products, describe what really differs: size, use, material, who it's for.
If you can't make them different, ask whether you need all of them. A single page listing every town you cover can do better than twenty copies.
Manufacturer descriptions
Shops often use the supplier's product text, which hundreds of other shops also use. Rewriting it in your own words, with your own details, gives Google a reason to show your page.
Checking your fix
Open each page side by side and check they now say clearly different things, or that the copies redirect to the main page.
If you use Duality, duplicate content depends on more than one page, so the next monthly audit confirms it.