What to Know About External Linking for SEO (and How to Get It Right)

External linking is one of the most misunderstood aspects of SEO. Even experienced marketers hesitate before adding outbound links, worried they might dilute authority, harm rankings, or send readers away at the wrong moment.

In reality, when external links are used well, they strengthen your content. They improve credibility, support a better reader experience, and reflect how the web is designed to work.

This guide breaks down what external linking really means for SEO. We'll look at what Google has said directly, how external links contribute to content quality, best practices for using them effectively, and common mistakes to avoid.

TL;DR: External Linking and SEO

• External links do not harm SEO when used correctly.
• They are not a direct ranking factor, but they support trust, credibility, and content quality.
• Pages with relevant, high-quality external links tend to perform better than pages without them.
• Best practices include purposeful placement, natural anchor text, and careful source selection.
• Link attributes matter for paid, user-generated, and non-endorsed links.
• External links should be reviewed and maintained over time to avoid broken or low-quality references.

What Are External Links?

External links (also called outbound or outgoing links) are hyperlinks that point from your website to a page on another website. When a user clicks one, they leave your site and visit an external source.

They play a meaningful role in SEO because they signal credibility and context to search engines. When you link to high-quality, authoritative sources, you reinforce that your content is well-researched and trustworthy (Market Brew).

They are different from:

• Internal links: links between pages on your own website
• Backlinks (inbound links): links from other websites pointing to yours

Every external link you publish is a backlink for someone else. This interconnected structure is the foundation of how the web works.

What Do External Links Mean for SEO?

The most common concern around external linking is the idea that linking out dilutes your site's authority. This belief leads some publishers to avoid external links entirely or apply nofollow by default.

Google has been clear on this point.

John Mueller has stated (Search Engine Journal):

"That's definitely wrong. It's definitely not the case that if you use normal links on your website that you would rank any worse than if you put nofollow on all outgoing links."

He has also explained that blanket nofollowing creates unnecessary problems. Publishers should be confident in the content they stand behind and use normal links where appropriate.

Are External Links a Ranking Factor?

No. External links are not a direct ranking signal.

Mueller has addressed this directly: "Nothing happens. Why should it? This has been one of those things that SEOs have claimed/hoped since literally decades." Referencing well-known sources does not compensate for weak content, or as he put it when asked whether linking to Wikipedia would help: "Name-dropping a dictionary doesn't fix your spelling mistakes."

However, this distinction matters: external links are not a ranking factor themselves, but they contribute to overall content quality, which Google does evaluate.

What the Evidence Shows

In 2016, Reboot Online conducted a controlled SEO experiment:

• Ten identical sites were created targeting invented keywords
• Five included three external links to authoritative sources
• Five included no external links

After five months, the sites with external links consistently ranked higher. The experiment was repeated in 2020 with the same outcome.

This does not prove that external links directly improve rankings. The sample was small and the conditions artificial. But the consistency across both runs is notable, and it does suggest that content supported by proper references and citations performs better, likely because it is more useful and trustworthy.

The takeaway is simple: strong content supported by credible sources tends to perform better than content that exists in isolation.

Danny Sullivan, Google's Search Liaison, reinforced this point: "I'd think of linking as just part of proper attribution. You're a journalist. You write a story, you cite your sources. If those sources are online with more info for the reader, that cite should link to them. That's just good journalism. It should be standard."

Why External Links Matter

If external links are not a direct ranking factor, why use them at all? Because they serve three important functions.

1. They Improve the Reader Experience

External links allow readers to verify claims, explore sources, and dig deeper where they choose. When you reference data, research, or expert opinions, linking to the source adds transparency and value.

2. They Support Credibility and Trust

Citing authoritative sources reinforces expertise and trustworthiness, key components of Google's E-E-A-T framework (Experience, Expertise, Authoritativeness, Trustworthiness).

Linking to high-quality sources shows that your content is grounded in real information and that you understand which sources matter.

Google's own documentation encourages this approach, noting that linking out to relevant sources can help establish trustworthiness.

3. They Connect Your Content to the Wider Web

No page exists in isolation. External links help place your content within a broader topical context, signaling how it relates to other information online.

Pages that never link out can appear self-contained or overly promotional. Thoughtful external linking makes your content part of a legitimate information ecosystem.

Five Best Practices for External Linking

1. Always Know Why You're Linking

External links should have a clear purpose. Most fall into one of two categories:

• Citation: supporting a claim, statistic, quote, or research
• Enrichment: offering additional context or deeper explanation

If a link doesn't serve one of these purposes, reconsider whether it's needed.

2. Choose High-Quality Sources

Before linking, evaluate the destination:

• Authority: recognised institutions, original research, reputable publications
• Accuracy: current and factually correct information
• Relevance: directly related to the point you're making
• User experience: avoid cluttered, low-quality, or misleading pages

Where possible, link to primary sources rather than aggregators.

3. Use Descriptive Anchor Text

Anchor text should clearly describe what the reader will find when they click.

Good anchor text:

• "Google's documentation on link attributes"
• "Reboot Online's external linking experiment"

Poor anchor text:

• "Click here"
• "Read more"

Keep anchor text natural and readable. Avoid forcing keywords into links.

4. Consider Placement and Flow

External links should support the content without disrupting it.

• Integrate links naturally into sentences
• Avoid clustering multiple links together
• Balance external links with internal ones
• Place important links early when they provide essential context

5. Don't Obsess Over Numbers

There is no ideal number of external links.

A short opinion piece might include none. A research-heavy article may include many. What matters is whether each link serves a purpose.

Signs you may have too many:

• Links feel forced or repetitive
• The page looks cluttered

Signs you may have too few:

• Claims lack supporting evidence
• Readers would benefit from additional context

Understanding Link Attributes

Link attributes explain the nature of a link to search engines.

Most editorial external links should not use any attribute. Use attributes intentionally, not as a blanket policy.

Google treats these attributes as hints, not directives, and they can be combined where appropriate (e.g. ugc sponsored).

Should You Link to Competitors?

Sometimes, yes.

Linking to competitors can make sense when:

• They have the best resource on a topic
• You're creating comparisons or roundups
• You're citing original research or data

Avoid linking when:

• The page is purely promotional
• A neutral third-party source works just as well
• The link directly competes with your conversion goals

Linking confidently to strong resources, even competitors, can reinforce credibility rather than undermine it.

Common External Linking Mistakes

Linking to Low-Quality Sources

External links act as implicit endorsements. Linking to spammy or inaccurate sites damages credibility.

Letting Links Break

External links decay over time. Broken links frustrate users and make content look neglected.

Audit links regularly and update, replace, or remove broken ones.

Using Nofollow by Default

Blanket nofollowing provides no SEO benefit and can look unnatural. Use it only when appropriate.

Linking to Paywalls Without Warning

If a link leads to a subscription or paywall, let readers know.

Maintaining Your External Links

How often you review links depends on site size:

• Small sites: quarterly audits
• Medium sites: monthly reviews
• Large sites: automated monitoring

Check for:

• Broken links
• Redirect chains
• Content that has changed significantly
• Domains that have declined in quality

How SEO Tools Can Help

For large or complex sites, managing links manually can be impractical. Many SEO platforms monitor external links as part of site auditing, flagging issues automatically.

Tools like Machined incorporate research-backed external linking into content workflows, helping ensure links are relevant, credible, and correctly placed without manual effort.

Final Thoughts

External links are a normal, healthy part of high-quality content. They don't dilute authority or harm SEO. Used thoughtfully, they improve trust, clarity, and usefulness.

Think like a journalist: cite sources, link where it adds value, and prioritise the reader. Content that connects to other good content is aligned with how the web, and search engines, actually work.

Link thoughtfully, link purposefully, and trust that good content benefits from connecting to other good content.

FAQs

Are external links bad for SEO?

No. External links do not harm SEO when used correctly. Google's John Mueller has explicitly stated that using normal outbound links will not cause your site to rank worse. In fact, pages with relevant, high-quality external links tend to perform better because they demonstrate credibility and provide value to readers.

Are external links a Google ranking factor?

External links are not a direct ranking factor. However, they contribute to overall content quality, which Google does evaluate. Research shows that pages with well-placed external links to authoritative sources tend to rank higher than equivalent pages without them, likely because they appear more useful and trustworthy.

How many external links should I include in a blog post?

There is no ideal number. The right amount depends on your content type and purpose. A short opinion piece might include none, while a research-heavy article could include 15-20. Focus on whether each link serves a clear purpose (citation or enrichment) rather than hitting a specific count.

Should I nofollow all my external links?

No. Blanket nofollowing provides no SEO benefit and can look unnatural to search engines. John Mueller has said this approach is "definitely wrong." Use nofollow only when appropriate, such as for unverified sources or content you don't want to endorse. Most editorial links should use no attribute at all.

Should I link to competitor websites?

Sometimes, yes. If a competitor has the best resource on a topic, is the source of original research, or you're creating a comparison piece, linking to them can strengthen your credibility. Avoid linking to purely promotional competitor pages or when a neutral third-party source would work equally well.

How often should I audit my external links?

This depends on site size. Small sites should audit quarterly, medium sites monthly, and large sites should use automated monitoring. Check for broken links (404 errors), redirect chains, content that has significantly changed, and domains that have declined in quality.