External linking refers to the set of practices by which a web page points to other resources published on different domains. In the context of Search Engine Optimization, the term is used mainly to describe the outbound links that a site places within its own pages to cite sources, further reading or authoritative references. It is therefore the mirror concept of link building, which concerns inbound links instead.
A well-managed external link can improve the reading experience, strengthen the credibility of a piece of content and help search engines understand the context of a page. Conversely, excessive or careless use of outbound links can distract the user and disperse the page’s authority. For this reason, managing external links is part of the ordinary work of anyone doing SEO.
Which links fall under external linking
External linking covers all hyperlinks that point to URLs outside the publishing domain. A blog post citing a study published on a university website, a product page linking to the manufacturer’s site or a guide linking to a software’s official documentation are all examples of external links.
In SEO literature these links are distinguished from internal links, which connect pages belonging to the same domain. The distinction is not only technical: it changes how search engines assess the passing of authority and it also changes user behavior, since the user leaves the site to reach a different resource.
Outbound links and inbound links: the difference
The two concepts are often confused, because both are described as “external links”. In reality the perspective changes completely depending on the point of observation. A link is outbound for the site that publishes it and inbound for the site that receives it.
What publishing a link to the outside involves
Whoever publishes an outbound link decides to direct part of the traffic toward a third-party resource. This choice affects the perceived quality of the page, the time spent on the site and the distribution of so-called internal authority.
What it means to receive a link from another site
Whoever receives an inbound link gains a signal of trust, which is stronger the more the source site is considered authoritative and topically related. Link building consists precisely in trying to obtain quality inbound links.
The technical characteristics that change a link’s behavior
External links differ based on some technical characteristics that modify their behavior. Knowing these differences is useful for choosing the most suitable solution for each individual case.
| Type | Behavior | Typical use | SEO effect |
|---|---|---|---|
| Simple link | Opens the resource in the same tab | Further reading within the reading flow | Passes authority to the destination page |
| Link with nofollow attribute | Opens the resource but signals not to follow it | Sponsored or unverified content | Does not pass authority directly |
| Link with sponsored attribute | Identifies a commercial relationship | Advertising and paid collaborations | Signals the promotional nature of the link |
| Link with ugc attribute | Indicates user-generated content | Comments, forums, reviews | Helps distinguish external contributions |
| Link with noreferrer attribute | Does not communicate the referring page | Privacy and security | Does not directly affect ranking |
Criteria for choosing and adding outbound links
There are no rigid rules on the number of external links to include on a page. There are, however, recurring criteria that help keep the content useful for readers and coherent for search engines.
- Link only to sources relevant to the topic covered, avoiding random references.
- Check that the destination page is reachable and still active.
- Prefer authoritative, primary or official sources when the information must be reliable.
- Place the link within meaningful text, avoiding generic phrases like “click here”.
- Limit the number of outbound links so as not to disperse the reader’s attention.
- Mark commercial or unverified links with the appropriate attributes.
- Periodically check already published links to remove those that no longer work.
- Keep consistency between the page content and the resource being linked to.
The most common mistakes and how to evaluate links
Among the most common mistakes is the habit of accumulating external links without a real informational need, in the belief that this increases the page’s authority. In reality, an excess of outbound links can reduce the perceived value of the content and drive the reader away too soon.
Another mistake is linking to low-quality or topically distant sites, which weaken the overall coherence of the page. Improper use of qualification attributes is also a problem, because incorrectly signaling the nature of a link can be interpreted as an attempt to manipulate search results.
The questions to ask yourself before publishing a link
Before publishing a link, it is worth asking some questions: does the resource add information the reader won’t find on the page? Is the destination site reliable and up to date? Is the link really necessary or repetitive? If the answer is positive, the link has a good chance of being an added value.
Frequently asked questions about external linking
What is the difference between external linking and link building?
External linking concerns the outbound links that a site publishes toward other resources. Link building, on the other hand, concerns the activity of obtaining inbound links from other sites to your own.
Do external links help ranking?
There is no automatic relationship between the number of outbound links and ranking. Relevant and authoritative links can improve the perceived quality of the page, but they do not replace solid, well-structured content.
How many external links can you include on a page?
There is no established numerical limit. Good practice suggests including only the links useful to the reader, avoiding accumulations that distract from the main topic.
When should you use the nofollow attribute?
The nofollow attribute is used when you do not want to pass authority to the destination page, for example for sponsored content, comments or resources whose reliability you cannot guarantee.
Does an external link make the site lose traffic?
It can happen if the link opens the resource in the same tab and the user does not go back. For this reason many sites open external links in a new tab, keeping the starting page open.
Should external links be checked over time?
Yes, it is advisable to periodically verify that the linked pages are still active and relevant. A link pointing to a resource that is no longer available worsens the reading experience and the credibility of the content.
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Outbound link Link Inbound link Example of a link SEO link