External links - the links your website sends out to other domains - are a part of SEO that many site owners overlook entirely. While most attention goes to earning backlinks from other sites, how and where you link externally also sends signals about your content’s credibility and thoroughness. Linking to authoritative, relevant sources can strengthen your content’s helpfulness in Google’s eyes, while linking to low-quality sites can do the opposite. This guide explains exactly how external links work and how to use them strategically.
TL;DR: Key Takeaways
- An external link is a hyperlink from your website that points to a different domain.
- Linking to high-quality, authoritative external sources can improve your content’s credibility and helpfulness signals to Google.
- External links do not directly hurt your SEO, but linking to low-quality or spammy sites can reflect poorly on your content quality.
- Use
rel="nofollow"for paid links, user-generated links, and links you do not want to vouch for. - Every external link is also a backlink from the perspective of the site being linked to.
What Is an External Link?
An external link is a hyperlink on your website that leads to a page on a different website or domain. When you cite a study by linking to the original research on a university website, add a reference to a news article, or link to a partner’s resource, you are creating external links.
This article is for website owners, content writers, and SEO practitioners who want to understand how external links affect SEO, when to use them, and how to do so correctly.
External links are one half of the link ecosystem that powers search engine optimization. The other half, backlinks, are links from other sites pointing to yours. Together, they form the web of connections that search engines use to evaluate credibility, relevance, and trustworthiness.
External Links vs. Internal Links vs. Backlinks
These three terms are often confused. Here is a clear breakdown:
| Term | Direction | Example |
|---|---|---|
| External link | From your site to another domain | You link to a research study on nature.com |
| Internal link | Between pages on your own domain | You link from a blog post to your services page |
| Backlink | From another domain pointing to your site | A news site links to your original research |
The same link is simultaneously an external link (from your site’s perspective) and a backlink (from the receiving site’s perspective).
Internal links help users navigate your site and distribute link equity between your own pages. See our guide on internal links for SEO for more detail.
Do External Links Help or Hurt SEO?
The short answer: linking out to high-quality, relevant sources generally helps your SEO. Linking out to low-quality or spammy sites can harm it.
How External Links Help
Credibility and trust signals: Google’s Quality Raters Guidelines evaluate whether content demonstrates trustworthiness. One indicator is whether claims are supported by credible sources. Citing reputable external references (government sites, academic journals, established publications) signals that your content is fact-checked and authoritative.
Relevance context: External links to topically relevant sites help search engines understand what your content is about and who the authoritative sources in your topic area are.
User experience: Linking to supporting resources makes your content more useful. Better user experience correlates with better engagement metrics (lower bounce rate, longer dwell time), which are indirect quality signals.
How External Links Can Hurt
Linking to low-quality sites: If you link to spammy, thin, or penalized domains, you can inadvertently associate your content with low-quality signals. Google evaluates the neighborhood your site operates in.
Excessive commercial linking: If a significant portion of your external links are paid or commercial links without appropriate disclosure, this can trigger spam detection.
Broken external links: Links that lead to 404 pages or inaccessible content create poor user experiences. Regularly audit external links to ensure they still work.
When to Use External Links
External links add value when they directly support or enrich the content for your readers:
Cite Your Sources
Any statistical claim, research finding, or factual assertion should be backed by a link to the original source. This serves the reader and demonstrates E-E-A-T (Experience, Expertise, Authoritativeness, Trustworthiness) to Google.
Example: “According to a 2024 Backlinko study, the first organic result receives an average CTR of 27.6%.” That statistic should link to the Backlinko study.
Reference Authoritative Definitions
When introducing a technical concept, link to a reputable definition or explainer if it adds value for the reader. This is particularly useful for topics where definitions are widely standardized.
Credit Original Sources
If you reference another creator’s work, data, or idea, link to the original. This is standard editorial practice and builds goodwill in your industry.
Provide Further Reading
Linking to complementary resources your readers might find useful extends the value of your content. Choose resources that are genuinely excellent rather than just convenient.
Best Practices for External Links
Follow these practices to get the most benefit from external linking while minimizing risk:
Link to Authoritative, Relevant Domains
Prioritize linking to established publications, official sources, academic institutions, government websites, and recognized industry leaders. Use tools like Moz or Ahrefs to check the domain authority of sites you link to.
Use Descriptive Anchor Text
Anchor text (the clickable text of a link) should describe what the linked resource is about. Avoid generic anchors like “click here” or “read more.” Descriptive anchors help users and search engines understand what the linked page covers.
See our guide on what is anchor text for detailed best practices.
Open External Links in a New Tab (Optional)
Many sites set external links to open in a new browser tab (target="_blank") to keep users on the site. This is a UX preference rather than an SEO factor. If you use it, also add rel="noopener noreferrer" for security.
Limit External Links Per Page
There is no hard limit, but 2 to 5 external links per 1,000 words is a reasonable guideline. Excessive external linking can dilute the focus of your page and create a poor reading experience.
Regularly Audit External Links
Linked pages go offline or change over time. Use a tool like Screaming Frog, Ahrefs, or a broken link checker plugin to identify and fix broken external links. Schedule this audit every 3 to 6 months.
External Link Attributes Explained
HTML link attributes tell search engines how to treat a link. Understanding them is essential for correct external linking practice.
rel="nofollow"
Tells search engines not to pass link equity (ranking credit) to the linked page. Use for:
- Links you cannot vouch for
- Paid or sponsored content
- User-generated content links
Example: <a href="https://example.com" rel="nofollow">anchor text</a>
rel="sponsored"
Introduced by Google in 2019. Specifically designates paid or affiliate links. Use for:
- Paid placements
- Affiliate links
- Sponsored content
rel="ugc"
Designates user-generated content links. Use for:
- Comment section links
- Forum links
- Review links
Default (no attribute)
An external link with no rel attribute is a standard dofollow link, meaning you are vouching for the destination and passing link equity. Use this for links you are actively endorsing.
See our guide on nofollow backlinks and their role in SEO for a deeper explanation of when nofollow matters.
Common External Linking Mistakes
Linking to Competitors Unnecessarily
While linking to authoritative sources is good practice, repeatedly linking to direct competitors can inadvertently send your readers to sites competing for the same keywords and conversions. Be selective.
Forgetting to Update Broken Links
Websites change. The URL you linked to 2 years ago may now return a 404. Regular audits prevent your content from pointing to dead ends.
Using Generic Anchor Text
“Click here,” “read this,” and “learn more” provide zero context. Always describe what the reader will find at the destination.
Linking to Redirect Chains
If a URL redirects multiple times before reaching the destination, link equity is lost with each hop. Link directly to the final destination URL where possible.
Ignoring Link Attributes for Paid Content
Any externally linked content you were compensated to include must use rel="sponsored" or rel="nofollow". Failure to disclose paid links violates Google’s Webmaster Guidelines.
Frequently Asked Questions
Does Google penalize for external links?
rel="nofollow" or rel="sponsored" can be used when you need to link out but do not want to associate your site’s reputation with the destination.How many external links per page is too many?
Should all external links be nofollow?
Do external links to high-DA sites boost my rankings?
What is the difference between an outbound link and an external link?
Conclusion
External links are a natural and valuable part of well-crafted web content. Linking to authoritative, relevant sources demonstrates credibility, supports your claims, and helps readers access additional useful information.
Follow a few key principles: link to reputable sources, use descriptive anchor text, apply appropriate link attributes (especially for paid or user-generated links), and audit your external links periodically to remove broken ones.
Used thoughtfully, external links strengthen your content quality and contribute to the trust signals that help your pages rank better over time.
Related reading: What Is a Backlink | What Is Anchor Text | Nofollow Backlinks and Their Role in SEO | Internal Links for SEO