An SEO silo structure was sold for years as a way to concentrate relevance: put every page on a topic in its own section, link only within that section, and the topic becomes a tidy, self-reinforcing block. Half of that advice holds up. Topic grouping is sound architecture. The isolation rule is the part that costs you links, readers and, in the worst case, pages Google never finds.
What is silo in SEO?
The definition most people work from is Semrush’s: “Silo SEO is a form of website architecture that involves grouping content by topic into self-contained sections of your website.” A gardening site might have one section for vegetables, one for lawns and one for tools, each with its own category page and its own set of articles underneath.
The strict version goes further. In Semrush’s words, “silos remain isolated and don’t link between each other.” An article about tomato blight links up to the vegetables hub and across to other vegetable articles, but never to the lawn section, even when a reader would plainly benefit.
That second rule is what separates a silo from ordinary topical organisation. Almost every well-run site groups content by topic. Far fewer forbid links between topics, and the ones that do usually do it because a course or a forum told them it would stop relevance leaking away.
The trade-offs of a strict SEO silo structure
Semrush’s own write-up is unusually balanced about the method. It lists real benefits and real costs, and the costs fall almost entirely on the isolation rule rather than on the grouping.
| Point Semrush lists | Pro or con | Our reading: caused by |
|---|---|---|
| Simpler structure for crawlers | Pro | Grouping |
| Logical navigation | Pro | Grouping |
| Concentrated topical coverage | Pro | Grouping |
| Limits internal linking | Con | Isolation |
| Artificial organisation | Con | Isolation |
| Risk of orphaned pages | Con | Isolation |
| Blocks useful connections between topics | Con | Isolation |
Look at the pros and every benefit comes from grouping. A crawler finds a clean hierarchy easy to follow whether or not sections cross-link. Readers like predictable navigation. Coverage concentrates because you plan by topic. None of those needs the wall between sections.
Look at the cons and nearly every cost comes from the wall. Even the artificial organisation is mostly a product of forcing each page into exactly one sealed box. That third column is our interpretation, not Semrush’s, but it is the useful finding here: you can keep everything good about a silo by keeping the structure and relaxing the linking rule.
Why the isolation rule backfires
Topics on real sites overlap. A post on lawn feed is relevant to a post on soil testing that lives in the vegetables section. A strict silo forces you to pretend they are unrelated. The reader who needed both has to find the second one through search or the menu, and often does not bother.
It also starves pages of internal links. Every page in a silo can only receive links from its own section, so a small section produces weakly linked pages. That is how strict silos manufacture the problem described in our guide to orphan pages: an article that belongs in one section but was never linked from it simply sits there with nothing pointing to it.
Depth is the third casualty. If the only route to a page is down through one hub, one category and one subcategory, the page ends up several clicks from the homepage. Cross-links are the usual way to shorten that path, and the silo forbids them. Our post on click depth explains why pages buried deep in a site tend to be crawled and valued less.
The leaking-relevance argument behind isolation was always more folklore than finding. Linking from a lawn article to a soil article does not make either page less about its topic. It tells Google, and the reader, how two topics relate.
Silo structure examples: the strict silo vs topic clusters
Semrush’s recommendation is to use topic clusters with pillar pages instead. A cluster keeps the grouping: one comprehensive pillar page per broad topic, with supporting articles linked to and from it. Unlike a strict silo, clusters are allowed to link to each other where it helps.
Here is the same gardening site both ways. In the strict silo, the tomato blight article links to the vegetables hub and to other vegetable pages only. In the cluster model, it links to the vegetables pillar, to sibling articles on other plant diseases, and across to the soil testing guide in the lawns cluster, because a reader dealing with blight will want to check their soil too.
The URL folders can look identical in both models. The difference is entirely in the linking policy, which is why a site can move from silo to cluster without a migration. If you want to build the pillar side properly, our guide to pillar pages covers the format, and the post on building topical authority covers how to plan the supporting articles around it.
How to fix an over-siloed site
If you inherited a strict silo, you do not need to rebuild it. Work through it in this order:
- Keep the existing sections and URL folders. The grouping is the part that works.
- Find pages with few or no internal links pointing to them, and link them from their own hub first.
- List the obvious overlaps between sections, where a reader of one page would genuinely need another.
- Add contextual links across sections for those overlaps, with descriptive anchor text.
- Check the click depth of your most important pages, and shorten long paths with cross-links.
Be selective with step four. The aim is not to link everything to everything, which dilutes the structure as badly as isolation weakens it. Link where the topics genuinely meet. Our guide to internal linking for SEO covers anchor text and placement in more detail.
The limitation is worth stating plainly. Nothing in the source material measures a ranking difference between strict silos and clusters, and we have no controlled test of our own to offer. The argument here rests on the mechanics: isolation blocks links and risks orphans, and grouping delivers the benefits on its own. Those mechanics are well understood, but how much a change moves your traffic will depend on the site. A small site with three tightly separated topics may see little difference. A large site where topics overlap constantly is where the wall does the most damage, and where taking it down is most likely to pay off. Make the change, watch the pages you linked, and judge from your own numbers rather than from a promise.
Frequently asked questions
What is a silo structure in SEO?
It is a site architecture that groups content by topic into self-contained sections. The strict version forbids links between those sections.
Is SEO silo structure still worth using?
The topic grouping is. The isolation rule is not: it limits internal linking, risks orphaned pages and blocks useful connections between topics.
What is the alternative to a silo?
Semrush recommends topic clusters built around pillar pages, which keep the grouping but allow linking between clusters where it helps the reader.
Do I need to change my URLs to move away from silos?
No. The difference is the linking policy, not the folders. You can keep your URLs and add cross-links between related sections.
The takeaway Keep the topic grouping that makes a silo useful, drop the rule that sections never link, and add cross-links wherever two topics genuinely meet.
