Quick answer: Internal links connect pages within your own website; external links point from your site to another domain (or from another domain to yours). For SEO, they serve different purposes: internal links pass authority around your site, guide crawlers to every page, and shape which pages rank for which queries. External links (backlinks) are votes of trust from other domains — valuable but outside your direct control. Internal linking is the one structural lever you can pull entirely on your own.

What internal and external links actually are

An internal link is any hyperlink where both the origin and the destination are on the same domain. A navigation menu, a "related products" strip, a text link inside a blog post pointing to a collection — all internal links.

An external link has two forms. Outbound: a link from your site to another domain. Inbound: a link from another domain to yours. In SEO, "backlinks" or "external links" almost always mean inbound links from other sites. Those are the ones that carry ranking weight.

Neither type is optional. A site without a coherent internal link structure leaves pages stranded. A site without any inbound links from other domains struggles to build the domain-level authority that helps competitive keywords.

How search engines use each type

Internal links: the crawl map and the authority circuit

Googlebot and other crawlers discover pages by following links. If a page has no internal links pointing to it, the crawler may never find it — or may find it rarely enough that it indexes slowly. Once a page is indexed, internal links also pass PageRank, the signal Google uses to judge how important a page is relative to others on your site.

Two things flow through an internal link: discoverability and authority. You control both.

External links (backlinks): domain authority from outside

A backlink from a relevant, trusted site tells search engines that your content has enough credibility for another publisher to reference. Accumulating these is slow, often expensive, and dependent on other people's decisions. You cannot fabricate genuine backlinks, and low-quality link schemes carry manual penalties.

Practical rule: Treat internal linking as infrastructure you build today; treat link acquisition as a campaign you run over months or years.

The asymmetry between them

Dimension Internal links External backlinks
Who controls it You, entirely Other sites and publishers
Time to implement Hours to days Weeks to months (or never)
Crawl impact Immediate once re-crawled Indirect; lifts domain authority over time
Cost Your time or a tool Often content marketing, PR, or budget
Spam risk Low if done naturally High if built artificially
Scales with catalogue Yes, with automation No — each link earned separately

Why internal linking matters more on ecommerce sites

A blog with twenty posts can get away with loose internal linking. A Shopify store with five hundred product pages cannot. The structural problem is arithmetic.

Your homepage is crawled constantly. Your top-level collections are linked from the homepage. But a product that sits inside a nested sub-collection — linked from a collection that is linked from a category that is linked from the homepage — may be four or five clicks deep before a crawler even reaches it.

Click depth and the three-click rule

Click depth is the minimum number of clicks required to reach a page starting from the homepage. Google's Gary Illyes and others at Google have noted informally that the deeper a page is, the less frequently it tends to be crawled. For ecommerce, a widely held working rule is:

Practical rule: Keep every product page within three clicks of the homepage — two clicks is better for your most commercially important pages.

This is not a confirmed algorithm threshold. It is a structural discipline that correlates with crawlability, faster index refresh, and in many cases better rankings for pages that were previously buried.

What "orphaned" means and why it matters

An orphaned page has no internal links pointing to it. Googlebot can only find it via sitemap, which is a fallback rather than a reliable crawl pathway. An orphaned product page is effectively invisible to internal PageRank distribution. Even if the product is excellent and the page is well-written, it starts at a structural disadvantage.

A worked example: collection to product on Shopify

Suppose you sell outdoor gear. Your store structure looks like this:

Homepage
└── /collections/tents
    ├── /products/2-person-ultralight-tent   ← 2 clicks deep ✓
    └── /collections/tents/expedition
        └── /products/base-camp-tent-6p      ← 3 clicks deep ✓ (borderline)
            └── [related products linked only from this page]
                └── /products/tent-footprint-6p  ← 4 clicks deep ✗

The footprint product is four clicks from the homepage. It gets crawled infrequently. It has almost no internal PageRank flowing to it. It probably ranks poorly despite being a product shoppers search for by name.

The fix has two parts:

  1. Add a "Pairs well with" or "You'll also need" section on the base-camp tent page that links to the footprint with descriptive anchor text: "compatible 6-person tent footprint."
  2. Link to the footprint from a relevant blog post — "how to care for your expedition tent" — using anchor text that matches how people search.

After both changes, the footprint is reachable in three clicks via the collection path, and two clicks via the blog post. Crawl frequency improves. PageRank flows to it from two directions.

Anchor text: the signal inside the link

The visible, clickable text of a link tells search engines what the destination page is about. Generic anchors ("click here", "learn more", "this product") waste that signal. Descriptive anchors ("6-person tent footprint", "waterproof groundsheet for expedition tents") reinforce the target page's topical relevance for those terms.

Practical rule: Write anchor text as if describing the destination to someone who cannot see the screen — specific, accurate, and brief.

Internal linking patterns for a Shopify catalogue

Pattern Where it works Watch for
Collection → product text links Collections with editorial intro text Don't link every product — prioritise high-margin or low-click-depth pages
Blog post → collection/product Any informational content Anchor text should match search intent, not marketing copy
Product page → related products "Frequently bought together", accessory sections Avoid linking every product to every other product (dilutes signal)
Product page → collection Breadcrumbs Ensure breadcrumbs are crawlable links, not JavaScript-only elements
Site-wide footer links Your most important collections Footer links carry less weight than in-body links; don't over-rely on them

What about external links you send out?

Outbound links — from your site to external domains — do not directly damage your rankings when used sensibly. Linking to a supplier's safety documentation, a relevant Wikipedia article, or a credible third-party resource is normal editorial behaviour. Search engines understand that sites link out to authoritative sources.

Two things to avoid: linking to low-quality or spammy domains (it can reflect on your own credibility), and using nofollow reflexively on every outbound link without reason. Nofollow is appropriate for paid placements or user-generated links you have not vetted, not for every citation in your content.

For Shopify stores, the ecommerce SEO practices that matter most — site structure, internal links, canonical tags — are covered in depth in our ecommerce SEO checklist for 2026.

How to audit your internal links without guessing

Identifying orphaned pages, click-depth problems, and thin anchor text manually across a large catalogue is impractical. You need a crawl.

Free options include Screaming Frog (crawls up to 500 URLs free), or connecting your store to Google Search Console for Shopify and reviewing the Coverage and Links reports. Search Console will show which pages have few or no internal links pointing to them.

For Shopify specifically, RankEngine audits a store's internal link structure and can write fixes back to the store through the Shopify Admin API — then re-reads the live store to confirm each fix actually landed before marking it resolved. That read-write-verify loop matters because Shopify themes sometimes strip or modify links written programmatically; an optimistic "done" state without verification gives you false confidence. One honest limit: RankEngine handles on-site signals only. It does not build backlinks — that is a separate, off-site discipline.

If you want to compare tools before committing, the best Shopify SEO apps for 2026 guide walks through what to look for.

How this connects to AI answer engines

AI answer engines — ChatGPT, Perplexity, Google's AI Overviews — cite pages they can crawl, parse, and trust. A page buried at click depth 5 with no internal PageRank flowing to it is less likely to be crawled frequently and therefore less likely to be cited. Internal linking is, indirectly, part of AI visibility.

If you are investing in answer engine optimization or want to understand how to improve your store's AI search visibility, the structural foundation is the same: every important page needs a clear crawl path, descriptive link text, and relevant content. No amount of structured data or llms.txt configuration compensates for a page that crawlers rarely reach.

Our complete Shopify SEO guide for 2026 covers how internal linking fits into the broader on-site picture alongside meta data, schema, and crawl configuration.

Summary

Internal links are the architecture of your site's authority. External backlinks are endorsements from the outside world. You build the first; you earn the second. For an ecommerce catalogue, internal linking is where neglect is most common and where the return on fixing it is most immediate — a product page that was five clicks deep and effectively invisible becomes a page that ranks once it is two clicks away and linked from relevant editorial content with accurate anchor text. Start there.