Why Links Matter for SEO
Links have been an essential part of SEO since the early days, before Google even existed. In those primitive times, keyword stuffing reigned supreme — the more a phrase appeared on a page, the higher it ranked. Unfortunately, practitioners gamed the system unnaturally, prompting search engines to seek a better evaluation method. Google emerged with PageRank, built on a simple but revolutionary assumption: important websites likely receive more links from other websites. Nearly three decades later, links remain core ranking factors, though the tactics for earning them have evolved considerably.
The foundational role of links in search evaluation became clear when Google founders Larry Page and Sergey Brin developed PageRank during their Stanford days. As Google's About page states, PageRank works by counting the number and quality of links to a page to determine a rough estimate of how important the website is. The underlying assumption is that more important websites are likely to receive more links from other websites. This link-based approach represented a fundamental shift from the keyword-stuffing era that preceded it, where the easiest way to rank was simply repeating a keyword phrase as many times as possible on a page.
Unfortunately, SEOs of that early era took advantage of the system, using keywords unnaturally by overusing the targeted phrase to rank higher. This method, now known as keyword stuffing, caused sites to rank for phrases even when they didn't have much to offer on a topic. A new way to evaluate sites beyond analyzing content alone was needed, and Google's PageRank provided that alternative by looking at the web's link structure instead.
Internal Links: Navigation and PageRank
Internal links connect pages within the same domain and help distribute PageRank across the site. Search engines determine whether a link is internal by looking at the domain name; if links point to other pages within the same domain, they're internal. If a site uses more than one domain, search engines will view those as external links.
These links aid user navigation and should prioritize user experience first, search engines second. Common areas for internal links include navigation menus, related-pages sections, user sitemaps, and in-content links. The homepage typically receives the most inbound links, so pages far from the homepage may see diminished PageRank before it reaches them. Since not all pages will get inbound links, internal links should serve two purposes: help users navigate to different pages of the site and help search engines crawl the entire site with fewer hops as possible from page to page.
Here are the common areas where you'll find internal links:
Normal site navigation — links usually located in a top bar menu, sidebar menu, and in the footer that exists on all pages. This is usually built upon your site architecture and how topics are categorized and subcategorized to build out topics and subtopics from general to specific pages.
Related pages — a section of a page that points out other pages that are related to the topic of the page. This is beneficial to users because it helps suggest pages the user was probably looking for.
User sitemaps — a sitemap is a single page that links out to all other pages of the site. Based on usability studies, there are three types of people that navigate a site: those who use the normal site navigation, those who immediately use the search box, and those who go straight to the sitemap. For very large sites, sitemaps can be overwhelming, and in cases like this, the sitemap may just contain the main category areas and not necessarily every page of the site.
In-content links — within the content of a page, links can be added to the words within a paragraph. This is under-utilized by many websites, but in other cases, it can also be over-optimized, which can have negative effects on SEO. Just link naturally and have the user in mind when building links like these.
Even though we're emphasizing the use of internal links in the distribution of PageRank, always make sure users are the highest priority. Always design sites and think of internal links for users first, then search engines second, and learn all best practices on internal site navigation.
Inbound (Back) Links: Votes of Trust
Inbound links from other domains are the most impactful for SEO, acting as votes of trust, credibility, and authority. The more natural links a page receives, the more votes it's getting, which can improve ranking. However, quantity alone doesn't matter — Google also evaluates link quality.
Google's Penguin update improved the algorithm's ability to identify artificial links more effectively. The Penguin update has now become an essential part of the core algorithm. Right after this update, some SEO professionals were initially under the impression that links no longer mattered; however, this is far from true. Links are important ranking factors and still indicate the same values as before. Links serve as a reflection of the quality of a page's content as long as they're natural links.
Nobody likes fake friends — sometimes you identify fake people right away. Other times, it isn't so easy. The same is true when Google looks at webpages. Links that seem like votes of trust can easily be faked using things like: online forums, blog comments, guestbooks, wikis, social media profiles, article directories, Q&A sites, and social bookmarking. These are called artificial links.
Sometimes, Google identifies that the links are fake right away, but not always. It can take Google a while to identify artificial links. These artificial links have negative consequences for the pages. The rank of these pages with artificial links can be hurt by various ranking factors monitoring link quality, as well as algorithm updates, or even manual actions from Google.
In order to have good, natural links, a site needs quality content that is trustworthy, credible, and authoritative. This allows the pages to gain quality, natural links from other websites, which will help their ranking.
Inbound links are still important even after Google's Penguin update. Over the past decade, Google has implemented a series of important algorithm updates. One of these important updates was Penguin. The Penguin update allows Google to evaluate the quality of links more effectively. Links have always been important ranking factors; however, the methods of obtaining links have evolved, especially after the Penguin update arrived. After the Penguin update, there is now a stronger emphasis on natural links, which made many SEOs in the industry focus a lot more on content marketing. Creating link-worthy content and promoting the content to the world to gain users that would be naturally willing to share and link to the content promoted.
Not everyone thinks like an SEO — don't overdo anchor text
One of the important aspects of inbound links that search engines pay attention to is the anchor text of a link. Anchor text is the clickable text of a link or the alternative text of an image in image links. The anchor text helps give search engines an idea of the topic of the destination page.
Historically, this was abused and made link bombing possible, which is simply using the exact phrase you want to rank for in all the inbound links' anchor text from thousands of webpages, regardless of the quality or relevancy of the page. Many previous Google updates addressed this issue, including the Penguin update, where overdoing keyword-focused anchor text can appear unnatural and may negatively affect ranking.
Ever since the Penguin update, there has been a strong focus on having natural anchor text in your inbound links. Here are a couple of things to look out for that may jeopardize your link building efforts:
Naturally, when people add a link on a page going to your website, often the anchor text will be your brand or company name. Thus, if your keyword-focused anchor text is more in quantity than your branded anchor text, this might cause problems. It is best to have more branded anchor text.
Not everyone thinks the same, and it is highly unlikely that a lot of people will use exactly the same anchor text. If you keep optimizing for the same anchor text when trying to gain links from other sites and it starts to become the majority anchor text and it is not your brand name, this is highly unnatural. It is important to see some diversity in anchor text, even including generic anchor text like "click here," "visit here," "website," etc.
Outbound Links: Appear Natural
Outbound links point from your site to domains with different names. For years, SEO pros believed outbound links leaked PageRank, prompting tactics like "PageRank hoarding" and adding nofollow to every outbound link. Google's 2009 PageRank evaporation update debunked that notion: hoarding simply doesn't work as it used to.
The current guidance is simple — link out if it's the natural thing to do. Linking to high-quality sites associates your site with quality signals in return. Overusing nofollow on all outbound links appears as PageRank hoarding and looks unnatural to search engines. The rule across all link types: appear natural. If it looks bad to humans, most likely it looks bad to search engines too.
Over the years, SEO pros have evolved how they use outbound links. Some believed that outbound links took away PageRank, decreasing its potential to rank. For some number of years, this may have been correct. This is where terms like "PageRank hoarding" and "PageRank channeling" came from. Any outbound link was the equivalent of a leak. But if an outbound link was necessary for users, you could add the nofollow link attribute. The nofollow was like telling search engines, "don't follow this link and give my PageRank to that page." However, many SEO practitioners abused this until Google came up with an update in 2009 on PageRank evaporation. In a nutshell, PageRank hoarding just didn't work like it used to.
Multiple theories and best practices have sprung out of this, such as:
Don't have too many outbound links: in theory, the whole reasoning of PageRank leaking still holds up to today. However, every once in a while, you may find sites with tons of outbound links, and yet the page still ranks high. Thus the rule here is just doing what seems to make sense.
Don't always nofollow all outbound links: adding a rel=nofollow attribute to links on the <a> tag tells search engines to not credit that link for ranking purposes. It makes sense to always add the nofollow to avoid PageRank leaking to other sites. However, overdoing or over-optimizing it just doesn't appear natural, and the intent appears to really be hoarding PageRank.
Good quality sites tend to link to good quality sites: giving links is just as important as getting links. Good quality sites are maintaining a level of quality that made them who they are, and thus if these sites are going to link out to other sites, they'd choose a good quality destination, too. Since this is common behavior on good quality sites, you might as well replicate that behavior to help show signals to search engines that you are a good quality site too.
In all these three bullet points, the rules may appear conflicting. No outbound links preserve PageRank, but no links at all look fishy. Adding a nofollow should help preserve PageRank. However, if links are all nofollow, they look more unnatural. Conventional wisdom taught us that outbound links leak out PageRank, and that is still true today, but it is recommended to link to good quality sites. The guidelines here don't seem to be set in stone and are somewhat flexible, but the main rule that is valid and applies to all rules above is to appear natural. Link out to other sites if it is the natural thing to do.
Linking Naturally: The Golden Rule
The consistent theme across inbound, outbound, and internal links is to link naturally. If a practice looks manipulative to a human reader, search engines likely devalue it too. Content marketing is now a primary way to earn natural links — creating link-worthy content and promoting it so users willingly share and link. In a world of algorithmic adjustments, the simplest guideline endures: link as you'd want to be linked to, and when in doubt, ask whether the link adds genuine value for a human reader.
Benj Arriola, Senior Digital Analyst at Adswerve, has been practicing SEO since 2004. Originally from the Search Engine Journal article "Why Links Are Important for SEO" (March 13, 2021).
