In just a little over two decades, search engine optimization, or SEO, has emerged as the dominant marketing tool. Given the wide dispersal of e-commerce, this is, in many ways, an understatement. Markedly, the web browser is the web’s information portal. But when combined with a search engine, a web browser is an information superhighway. To put things into a much-needed perspective, we need to understand where that superhighway goes.
- There are about 1.74 billion websites on the Internet
- 359.8 million registered domain names 
- 600 million blogs and 1.7 of those are in the U.S.
- Every day there are about 7 billion Google searches.
While these four staggering numbers are just a small portion of Internet statistics, it is easy to see why SEO is a dominant marketing tool. Given this, do multiple domains help SEO? The simple answer is yes and no. This blog discusses when multiple domains help SEO and when they don’t.
When to Use Multiple Domains
In the early days of e-commerce, buying multiple domains and pointing them to a main website was advantageous. In the pre-Google years, a business could get away with duplicate content and not get put on a blacklist. However, given Google’s advanced algorithms, a savvy SEO marketer can develop a multiple domain strategy that bypasses Google’s duplicate content rules.
Many big businesses use a multiple domain strategy to dominate search engine results pages (SERPs). This strategy keeps Google from blacklisting your sites. And, as Dod notes, “multiple sites can also help you to take up more Google real estate.”  The key to using a multiple domain strategy comes from one company owning two or more companies. Trulia and Zillow, for example, are both owned by the same company. Together they are a real estate brand with related but different keywords ranking both.
A multiple domain strategy does not work for all businesses. However, if you’re selling a brand with multiple related niches, a multiple domain strategy works. In this volatile world of filling eCommerce niches, brands frequently buy other brands. Instead of combining the brands into one brand, it is advantageous to keep the brands separate. This is particularly true if both brands have substantial popularity and have well-known domains.
When Not to Use Multiple Domains
If you buy multiple domains and point them back to a main website, you run the risk of being penalized by Google. Even if you park both domains together on the same website, Google still sees them as separate websites. Google will then flag them as duplicate content, which lowers the SERPs. As Dod notes, “The biggest drawback of having multiple sites is that you are splitting up your link authority between them.” There is a workaround. For example, you could use a 301 redirect, or a set of instructions on the server that redirects the domain request to a different page. But, if you’re willing to employ this strategy, you must double your marketing efforts.
Google’s search engine algorithms are complex, and multiple domains could end up confusing Google, thus lowering your SERPs. Therefore, if you want the best bang for your marketing buck, only use multiple domains in specific marketing instances.
 Ahlgren, Matt. September 20. 2020. 100+ INTERNET STATISTICS AND FACTS FOR 2020. https://www.websitehostingrating.com/internet-statistics-facts/
 Verisign Q3 Domain Brief. December 19, 2019. https://blog.verisign.com/domain-names/verisign-q3-2019-domain-name-industry-brief-internet-grows-to-359-8-million-domain-name-registrations-in-the-third-quarter-of-2019/
Dod, Ron. Multiple Sites: Does It Hurt or Help SEO? September 14, 2017. Search Engine Journal. https://www.searchenginejournal.com/multiple-sites-hurt-help-seo/208429/#close