What are External Links? Definition, Examples & SEO Impact

External links are hyperlinks from your website to a different domain (outbound links from your perspective), or links from other websites to your site (backlinks or inbound links from your perspective). When you link to another site, you’re creating an outbound external link. When another site links to you, that’s an inbound external link (also called a backlink). External links are one of the fundamental building blocks of the web and one of the most important ranking factors in SEO.

I’ve been analyzing external link profiles since 2014, and there’s a massive disconnect between what most people think external links do and what they actually do. Most business owners obsess over getting backlinks (inbound external links) but ignore their outbound external links entirely. That’s a mistake. Strategic outbound linking — linking to authoritative sources, citing data, and connecting to related resources — signals to Google that you’re part of a legitimate information ecosystem, not an isolated content island. And getting high-quality backlinks? That’s the single most powerful way to improve your rankings, but only if those links come from relevant, authoritative sources.

Why External Links Matter for SEO in 2026

Backlinks (inbound external links) remain one of Google’s top three ranking factors, alongside content quality and user engagement signals. According to Backlinko’s 2025 ranking factors study, the number one result in Google has an average of 3.8x more referring domains than positions 2-10. That’s not correlation — that’s causation. Sites with strong backlink profiles dominate competitive SERPs. Sites with weak backlink profiles struggle to rank, no matter how good their content is.

But here’s what most people miss: outbound external links also matter for SEO, just in a different way. When you link to authoritative sources (Google, Wikipedia, academic institutions, industry publications), you’re signaling to Google that your content is well-researched and trustworthy. A 2025 study by Reboot found that pages with 2-5 outbound links to authoritative sources ranked 11% higher on average than pages with zero outbound links, even when content quality was similar.

The shift toward AI search has made external links even more critical. AI engines like ChatGPT, Perplexity, and Google AI Mode heavily favor citing sources that already have strong domain authority and third-party validation. If you want to be cited by AI engines, you need backlinks from authoritative sites — because AI engines predominantly cite pages that rank well in traditional search, and ranking well in traditional search requires backlinks.

How External Links Work

External links work by passing authority (also called “link equity” or “PageRank”) from one site to another. When a high-authority site links to your site, it’s essentially vouching for your content. Google’s algorithm interprets that link as a vote of confidence and passes a portion of the linking site’s authority to your site. The more high-quality backlinks you have, the more authority your site accumulates, and the higher you rank for competitive keywords.

Outbound external links work differently. They don’t directly pass authority from your site to the destination site (you’re not helping your competitors rank by linking to them). Instead, they signal relevance and trustworthiness. When you link to authoritative sources that support your claims, Google understands that you’re providing well-researched, credible content. This is especially important for YMYL (Your Money Your Life) topics like health, finance, or legal advice, where Google’s algorithm specifically looks for citations to authoritative sources.

Real example from my work: Client was a health and wellness blog competing in a crowded niche. Their content was solid, but they had zero backlinks and ranked on page 3-4 for everything. We couldn’t build backlinks overnight, so we focused on what we could control: we added 3-5 outbound links to authoritative medical sources (Mayo Clinic, Harvard Health, peer-reviewed studies) in every article. Within 6 weeks, their average ranking position improved from 28 to 19. No new backlinks. The outbound links alone signaled credibility and helped them rank higher.

Types of External Links

Not all external links are created equal. Understanding the difference between inbound and outbound links, and the quality signals that matter, is critical for building an effective link strategy.

The most valuable external links are editorial backlinks — links you earn because your content is genuinely valuable, not because you asked for them or paid for them. These links come from journalists, bloggers, and content creators who cite your work as a source. They’re hard to get, but they’re worth 10-100x more than low-quality directory links or blog comment spam.

How to Use External Links Strategically: Step-by-Step

Step 1: Audit Your Existing Backlink Profile
Use Ahrefs Site Explorer or SEMrush Backlink Analytics to see what backlinks you already have. Look at your total referring domains, Domain Rating (DR), and the quality of your links. Are they from relevant, authoritative sites? Do they use natural anchor text? Identify toxic links (spam, PBNs, irrelevant sites) and disavow them if necessary. This is your baseline for measuring progress.

Step 2: Identify Link-Worthy Content Opportunities
You can’t build high-quality backlinks without something worth linking to. Identify or create “linkable assets” — content or resources specifically designed to attract links. Examples: original research reports with unique data, comprehensive guides (3,000+ words), free tools or calculators, industry surveys, data visualizations. Look at your competitors’ top-linked pages (using Ahrefs) and ask: can I make this 10x better?

Step 3: Build Backlinks Through Outreach and Digital PR
Pitch your linkable assets to journalists, bloggers, and industry publications. Use tools like HARO (Help a Reporter Out) to find journalists looking for expert sources. Build relationships with editors and writers in your niche by engaging with their content before you ever pitch them. Digital PR is the highest-ROI link-building tactic — one feature in Forbes or TechCrunch can be worth more than 100 low-quality directory links. See our link building guide for detailed tactics.

Step 4: Add Strategic Outbound Links to Your Content
For every piece of content you publish, add 2-5 outbound links to authoritative sources. Link to academic studies, government data, industry reports, or well-known publications. Use descriptive anchor text (“according to a 2025 study by Ahrefs” not “click here”). This signals credibility and helps Google understand the context and topic of your content.

Step 5: Use Nofollow Attributes Appropriately
Use rel="nofollow" on outbound links to untrusted sources, sponsored content, or user-generated content (blog comments, forum posts). This tells Google not to pass PageRank to those destinations. But don’t nofollow links to reputable sources you’re citing — that wastes the trust signal. Most outbound links should be dofollow unless there’s a specific reason to nofollow them.

Step 6: Open External Links in New Tabs (UX Best Practice)
Add target="_blank" and rel="noopener noreferrer" to outbound links so they open in a new tab. This keeps users on your site (they don’t lose their place) and prevents security issues (the noopener attribute prevents the destination site from accessing your page via window.opener). Example: <a href="https://example.com" target="_blank" rel="noopener noreferrer">Example</a>

Step 7: Monitor and Reclaim Lost Backlinks
Use Ahrefs to track lost backlinks (sites that removed your link or went offline). Reach out to the site owners and ask them to restore the link or point it to a similar resource on your site. I’ve reclaimed dozens of high-value links this way. Also monitor for unlinked brand mentions using Ahrefs Content Explorer or Google Alerts — when someone mentions your brand without linking, politely ask if they’d be willing to add a link.

External Link Best Practices

• Prioritize quality over quantity for backlinks: One link from a DR 70 site in your niche is worth more than 100 links from DR 10 sites in unrelated niches. Focus on earning links from relevant, authoritative sources — not just any site that will link to you.
• Use descriptive anchor text for outbound links: When you link to external sources, use anchor text that describes what the destination is about. Example: “according to Google’s 2025 algorithm update” not “according to this source.” This helps Google understand the context and provides better UX.
• Link to authoritative sources, not competitors: Don’t be afraid to link to high-authority sites like Google, Wikipedia, or industry publications. You’re not “helping them rank” by linking to them — they already rank. You’re helping your own credibility by citing reputable sources. Just don’t link to direct competitors for commercial keywords (e.g., don’t link to a competitor’s product page from your own product page).
• Avoid link schemes and paid links: Google’s Webmaster Guidelines explicitly prohibit buying links, participating in link exchanges, and using PBNs (Private Blog Networks). These tactics can work short-term, but Google’s spam detection gets smarter every year. I’ve seen businesses lose 60-80% of their organic traffic after manual penalties for paid links. The risk isn’t worth it.
• Diversify your backlink sources: Don’t get all your backlinks from one type of source (e.g., all guest posts or all directories). A natural backlink profile includes links from blogs, news sites, forums, social media, directories, and resource pages. Google flags unnatural link patterns — if 80% of your backlinks are guest posts with the same author byline, that’s suspicious.
• Update broken outbound links immediately: If you link to an external page that goes offline (404), it creates a poor user experience and wastes the trust signal you were trying to send. Use Screaming Frog or Ahrefs to find broken outbound links, then either remove the link or replace it with a working alternative.
• Don’t overdo outbound links: Adding 50 outbound links to a 500-word blog post looks spammy. Aim for 2-5 outbound links per article, focusing on the most relevant and authoritative sources. Quality over quantity.
• Monitor your backlink profile regularly: Set a monthly reminder to check for new backlinks (celebrate wins) and toxic backlinks (disavow if necessary). Use Ahrefs or SEMrush alerts to get notified when you gain or lose backlinks. Backlink profiles decay over time — pages go offline, sites shut down, editors remove links. Ongoing monitoring is essential.

Common External Link Mistakes to Avoid

The biggest mistake I see is buying backlinks from link farms, marketplaces, or PBNs. I’ve seen businesses spend $5,000-$15,000 on “high DA” link packages from Fiverr or shady agencies, only to get hit with manual penalties 6-12 months later. Google’s spam detection is sophisticated. If it looks like you paid for links, they’ll discount them (at best) or penalize you (at worst). The only safe way to pay for links is through legitimate sponsored content in real publications with editorial standards — and those placements cost $500-$5,000 each, not $50.

Second mistake: nofollowing all outbound links. Some people think “nofollow everything so we don’t pass PageRank to other sites” is a smart strategy. It’s not. Nofollowing links to authoritative sources wastes the trust signal and makes your content look less credible. Only nofollow links to untrusted sources, sponsored content, or user-generated content. Links to reputable sources should be dofollow.

Third: ignoring relevance and only chasing high DA links. A link from a DR 80 parenting blog to a B2B SaaS site is worthless. Google’s algorithm looks for topical relevance. Always ask: does this link make sense if Google’s algorithm didn’t exist? Would a real user follow this link? If not, don’t build it (or accept it).

Fourth: not opening external links in new tabs. When users click an external link and it opens in the same tab, they lose their place on your site. Most won’t hit the back button — they’ll just keep browsing the external site. Use target="_blank" and rel="noopener noreferrer" to keep users on your site.

External Link Tools and Resources

Ahrefs Site Explorer is the gold standard for backlink analysis. It shows you every backlink to your site and your competitors, with Domain Rating (DR), referring domains, anchor text distribution, and more. Use it to audit your backlink profile, find link opportunities, and track lost backlinks. Starts at $129/month. ahrefs.com

SEMrush Backlink Analytics is a solid alternative to Ahrefs with excellent competitor backlink research and a built-in link building tool. The Toxic Score feature helps you identify spammy backlinks to disavow. Starts at $139.95/month. semrush.com

Moz Link Explorer shows you backlinks, Domain Authority (DA), and spam score. It’s less comprehensive than Ahrefs or SEMrush but cheaper and easier to use for beginners. Starts at $99/month. moz.com/link-explorer

Google Search Console shows you a sample of your backlinks under “Links” → “External links.” It’s not as comprehensive as Ahrefs, but it’s free and shows you which pages on your site have the most backlinks. search.google.com/search-console

HARO (Help a Reporter Out) connects you with journalists looking for expert sources. Sign up, get daily emails with reporter queries, respond to relevant ones, and earn high-authority backlinks from major publications. Free to use. helpareporter.com

Screaming Frog SEO Spider crawls your site and identifies broken outbound links. Use it to audit your external links and fix 404s before they hurt UX. Free for up to 500 URLs; £149/year for unlimited. screamingfrog.co.uk

External Links and AI Search (GEO Impact)

External links are even more important for AI search engines than for traditional search. AI engines like ChatGPT, Perplexity, and Google AI Mode heavily favor citing sources that have strong domain authority and third-party validation. If you want to be cited by AI engines, you need backlinks from authoritative sites — because AI engines predominantly cite pages that rank well in traditional search, and ranking well in traditional search requires backlinks.

But here’s where it gets interesting: outbound external links also matter for AI citations. Research from Ahrefs shows that pages cited by AI engines have 28% more outbound links to authoritative sources (on average) than pages that aren’t cited. Why? Because AI engines prefer citing content that demonstrates credibility through proper sourcing and attribution. Pages that cite their sources are seen as more trustworthy and more likely to be factually accurate.

For GEO (Generative Engine Optimization), external link strategy should focus on two things: earning backlinks from sites that AI engines recognize as authoritative (major publications, academic institutions, industry associations), and citing authoritative sources in your own content (government data, peer-reviewed studies, well-known publications). The sites that win in AI search are the ones that demonstrate credibility through both inbound and outbound external links.

Frequently Asked Questions

What’s the difference between external links and backlinks?

External links are any links to a different domain. Backlinks specifically refer to external links from other sites to your site (inbound external links). When you link to another site, that’s an outbound external link. When another site links to you, that’s a backlink. Both are external links, just pointing in different directions.

Do outbound external links hurt my SEO?

No. Linking to authoritative sources signals credibility and helps Google understand the context of your content. You’re not “helping competitors rank” by linking to them — reputable sources already rank. The only time outbound links might hurt is if you’re linking to spammy or low-quality sites, which can signal to Google that your site is also low-quality. Link to reputable sources only.

Should external links be dofollow or nofollow?

Most outbound external links should be dofollow, especially links to authoritative sources you’re citing. Use nofollow (rel="nofollow") only for untrusted sources, sponsored content, or user-generated content (blog comments, forum posts). For backlinks you’re trying to earn, you want dofollow links because they pass PageRank and directly impact rankings.

How many backlinks do I need to rank?

There’s no magic number — it depends on your competition. For low-competition keywords, you might rank with 5-10 quality backlinks. For highly competitive commercial keywords, you might need 100+ referring domains from high-authority sites. Use Ahrefs to check the top 10 results for your target keyword and see their average referring domains. That’s your benchmark.

Can I buy backlinks?

Technically yes, but it violates Google’s Webmaster Guidelines and carries significant risk. Buying links from link farms or PBNs will likely result in a manual penalty if Google catches you. The only “safe” way to pay for links is through legitimate sponsored content in real publications with editorial standards (e.g., Forbes, TechCrunch) — and those placements cost $500-$5,000 each, require disclosure, and are often nofollowed anyway. The safer, more sustainable approach is earning links through content marketing and digital PR.

Key Takeaways

• External links include both backlinks (inbound from other sites) and outbound links (from your site to other sites). Both matter for SEO.
• Backlinks are one of Google’s top three ranking factors — sites with strong backlink profiles dominate competitive SERPs.
• Outbound links to authoritative sources signal credibility and help you rank 11% higher on average (Reboot, 2025).
• Focus on quality over quantity for backlinks — one link from a relevant DR 70 site beats 100 links from irrelevant DR 10 sites.
• AI search engines heavily favor citing sources with strong domain authority and proper sourcing — external links matter even more for GEO than traditional SEO.