Myth Busting: Will Duplicate Schema Tags Hurt Your SEO?

In the world of SEO, duplicate content has been one of the biggest concerns since the 2011 Panda algorithm update. However, it isn’t the only form of duplication that can impact a site. There’s a lot of nuance and many edge cases that may or may not hurt your site overall, but it’s still a largely visible (and understood) problem.

One form of duplication is in metadata. Specifically, Schema tags. Can duplicate Schema tags hurt your SEO? Let’s find out.

What is Schema and How Does It Work?

To understand how duplicate Schema tags might impact your site’s SEO, you need to know what Schema is in the first place.

Schema is the overall name for a kind of structured data markup that lives in website metadata. It’s invisible to the user but visible to the search engines, who can then use it in whatever way they want.

Schema has been a collaborative effort by Google, Microsoft, Yahoo, Yandex, and other community members throughout the years since it was introduced. It’s essentially a vast library of markup language and attributes, which allow you to tag elements of your site (everything from a single number to a whole page) and give it greater context.

Consider this: Google scrapes your website and finds a product page. It sees three numbers on the product page. These three numbers are the quantity available, the price per unit, and the SKU.

How does Google know which number is which?

There are a lot of answers to this. They can look at the surrounding words and symbols. If they see a $ or a €, they can reasonably assume that it’s a price. If they see the word “SKU,” they know that number is probably the SKU. Context gives a lot of information.

What about sites that aren’t formatted that way? Sites that use scripts to pull information from a database rather than render it on the page? Sites that put the numbers in a table, so the elements are separated in the HTML? It gets a little harder to identify what number is what.

This phenomenon is why, very rarely, you’ll find a product that costs some obscene number in Google Shopping; because Google pulled the SKU, thinks it’s the price and lists that as the price.

Google is highly sophisticated and very rarely makes these mistakes. The other search engines follow suit, though they aren’t quite as good at it.

That’s just one example, though. Now think about all the other kinds of context that might be relevant to the information on a page.

• A star rating. Is it for the article or for something you’re reviewing? For the page itself? An unrelated example?
• Fact-checking. Flagging part of a page as a claim and the rest as verified, checked facts are much more complicated than identifying a few numbers.
• Do you know how some Google searches have drop-down boxes with questions and answers pulled from sites? How does Google know when these are relevant question and answer pairs? The solution is Schema markup.

When you look at Schema.org to read what kinds of schema exist, you probably shouldn’t be surprised to see this (as of the publication of this post, anyway):

“The vocabulary currently consists of 797 Types, 1453 Properties 14 Datatypes, 86 Enumerations and 462 Enumeration members.”

That’s a lot of attributes!

Of course, the average website isn’t going to use the vast majority of them. A lot of them are specific and, often, mutually exclusive. Many of them are meant for sites like IMDB, where they can tag all of the information about a given movie or piece of media, and Google can pull that information for their knowledge graph.

Of course, business blogs (product pages, service pages, About pages, Contact pages, and more) can use some Schema elements. That’s why it’s been such an important topic over the last few years and why people are increasingly concerned with things like duplicate schema tags.

What Are Duplicate Schema Tags and How Do They Happen?

A single schema tag on a page will (usually) be tied to a piece of information on the page. To keep with the IMDB example, the line where a name is filed under “Director” will have a schema tag that says “Director” and type: Person and name: Director’s Name.

Of course, this information isn’t usually tagged in that line in the HTML for ease of management. Instead, it’s all lumped into one big mass of Schema tags for everything on the page, all up in the site’s <head> tag.

How does it get there?

Most of the time, web admins use a plugin to manage it. This solution might be a custom plugin, or it might be a plugin like WP Schema or Schema for WordPress, or it might be part of a more extensive SEO plugin like Rank Math.

Sometimes, particularly for non-WordPress sites, it might also be code generated using a website-based tool like this.

Duplicates happen for a few reasons, primarily.

1. The first is when more than one plugin or tool is being used. A food blog on WordPress might use WP Schema Pro but also utilize WordPress Recipe Manager, which has built-in Schema support. Both of them generate Schema tags for the individual elements of the recipe, from ingredients to tools to steps to the name. The resulting site has the same Schema data on it.
2. The second is when an automatic plugin is used, but a well-meaning webmaster also uses a manual tool to insert it. This option is the riskier of the two, for reasons you’ll see when we get a bit deeper into the topic.
3. A third potential reason is a page-based overlap. For example, you might put a site-wide footer with your business contact information and NAP in it, and to facilitate SEO visibility, you attach Schema markup to it. On your Contact page, you also have your NAP and contact info and Schema attached to it. But, that Contact page also has your site footer, so it has two copies.

Perhaps a more standard version of the same issue is using an eCommerce platform with built-in Schema for product information and using a secondary plugin to manage Schema and fill out the info there.

In either of these cases, you should run your website through Google’s Schema Markup Testing tool, found here. It will help you identify duplicate Schema tags and resolve the issue.

Does Duplicate Schema Hurt Your SEO?

Now to the question: does having duplicate Schema tags hurt your SEO?

The simple answer here is “no,” and there’s a good reason for that: Schema isn’t a ranking factor.

Don’t believe us? Read this analysis from the Search Engine Journal. They cite multiple sources at Google who directly state it: using Schema does not improve your search ranking.

At least, not directly, and that’s the crux of the whole issue.

Schema isn’t used in your search ranking. What it is used for, though, is almost as important.

• It allows Google to show additional search enhancements in their SERPs, like sitelinks, rich information, or excerpts.
• It allows Google to populate its search results more accurately. While it might not improve your ranking, it can potentially improve your click-through rates.
• It gives you better visibility in tertiary searches, like Google Shopping.
• It helps you show up as “position zero” or in the knowledge graphs.

If you and another site had identical content and backlink profiles – similar metrics, age, and authority, so we can theoretically isolate Schema – and you used Schema, but the other website didn’t, you wouldn’t rank any higher than they would. You might have a more attractive-looking search result, which would result in higher click-through rates.

How Google Parses Schema

Another exciting aspect of Schema is how Google (and, by extension, likely the other search engines) parse it in the first place.

There’s a rundown of the process here from Ilana Davis, an expert in Schema and developer of one of the better tools for implementing it. You can read the full rundown at that link, but here’s a quick summary.

1. Google scrapes a URL and throws all of the data – from your H1 tags to your image alt text to your Schema – into a bucket for analysis.
2. They identify the overall kind of Schema being used. It might be Product, Movie, Review, or whatever else; that top-level category determines what attributes and elements should be on the page and what ones are not valid.
3. They filter the data for anything not relevant. For example, schema tags that don’t go to the overall Schema are just discarded. Likewise, if you have a store and the products in your “people also buy” widget also have Schema attached, all of that data will be discarded, and you will use only the Schema for the primary product.
4. They look for a complete set of Schema available on the page. If there’s a set that fills out every attribute, they use that. If there are two, and one is incomplete, they discard the incomplete one.
5. If no complete set exists, and if more than one incomplete set exists, they’ll pick the one that has more relevant data. Sometimes they’ll synthesize the two together (if they cover each others’ gaps), but most of the time, they pick one with more crucial data.
6. Google may discard anything with mistakes. If nothing works, they look for the Schema that is free of errors. However, if your Schema has warnings, that might not matter or affect how your Schema appears on Google’s search results. Warnings are pretty typical; for example, if you decide not to fill out an optional field, it will trigger a warning, but your rich snippets will still appear on Google’s search results.

Errors will see your Schema discarded entirely, which is why validating your Schema when you publish it is essential.

You might notice that duplicates aren’t a cause for Schema to be discarded. Errors are, but duplicated tags are not considered an error.

The Bad Information Problem

One issue can cause your Schema to be discarded due to duplication. When you have two different Schema implementations on the same page, and they both cover the same set of information but have conflicting information, that can cause problems.

A simple example would be your product pages. If you have a set of Schema generated automatically from your product database and one that you update manually, they can get out of sync. Things like SKUs aren’t likely to change, but prices can. If Google looks at your site and sees Schema defining two different prices for the same product, which one do they choose?

Well, Google can look at your HTML, decide which price is displayed to the user, and pick that Schema. OR, they can discard the Schema entirely. Usually, it’s that second one.

Again, though, this doesn’t hurt your SEO directly. It hurts your eligibility for Google’s Merchant Center and your appearance in Google Shopping and other rich results, but it doesn’t hurt your site’s overall search ranking.

Myth Busted

So, there you have it. If you use Schema, you can gain benefits through the knowledge graph and other rich results, but you necessarily don’t gain any direct SEO benefits. If you accidentally have duplicate Schema tags, 99% of the time, you don’t have to worry about them, as long as the information on them is well-formed and identical. If there’s a disparity, Google will ignore them, but that won’t tank your site; it just means you won’t get all of those delicious rich results.

Generally, all you need to do is run your site through one of their recommended Structured Data Validators. As long as Google says there are no errors, you’re fine. If errors show up, then you need to fix them. It’s as simple as that.

Do you have any other questions or myths about SEO you want to be investigated and either confirmed or busted? If so, please let us know, and we’ll take a look. Or, if you’re concerned about your site’s Schema implementation, please get in touch with us! We’re happy to help you optimize your website and improve your traffic site-wide.