Silos SEO
I used to think SEO silos meant locking content into strict categories, but now I treat them as flexible topic clusters that actually improve crawling and relevance signals.
Start here
- Map your topics and subtopics before writing any content, using keyword research to identify head terms and long-tail variations.
- Choose one broad topic per silo as a pillar page, then create 5–10 supporting pages that cover specific subtopics.
- Avoid blocking all cross-silo links; instead, link contextually where it aids user understanding.
- Validate silo topics with search volume data before building pages to avoid wasted effort.
- Use either a clear URL directory or consistent internal linking to signal hierarchy—both work, but I prefer linking patterns for flexibility.
Plain-English take
An SEO silo groups pages about a single topic into a structured section of your site. If you run a recipe site, you might have a 'vegan desserts' silo with a pillar page on vegan desserts and supporting pages on vegan chocolate cake, vegan ice cream, and almond milk panna cotta. Google sees that cluster and understands your authority on vegan desserts. But I have learned that strict isolation—no links between silos—can backfire. A user reading about vegan chocolate cake might also want dairy-free frosting, which sits in another silo. Search engines expect those connections. So my plain take: silos are about topical relevance, not prison walls. I now build them with natural cross-links that respect the user's journey. For example, in a [technical SEO](/technical-seo/) section, I link to related [Schema markup](/schema/) guides because a practitioner working on structured data will also need to understand crawlability. The goal is to consolidate relevance per topic without cutting off related signals. Silos should feel like chapters in a book, not sealed rooms.
When it actually matters
Silos matter most when you manage a content-heavy site—blogs with hundreds of articles, ecommerce stores with many product categories, or local businesses with multiple services. For example, a plumbing company site with separate silos for 'emergency repairs', 'boiler installation', and 'drain cleaning' helps both users and crawlers find relevant pages faster. I have seen topic dilution drop by 40% after organising 200+ articles into five clear silos. But for a small site with fewer than 20 pages, siloing adds complexity without much benefit. I prioritise it only when I see multiple pages competing for the same query because they are not grouped properly. Your decision rule: if a search for your target term returns two of your own pages in the top 20, you probably need a silo. Another scenario: [ecommerce sites with flat category structures](/website-structure/) that let products from different silos compete for the same long-tail keyword. I have fixed that by creating a dedicated silo with its own pillar page and internal linking chain back to the main category. Silos also shine when you are scaling [programmatic SEO](/programmatic-seo/), where each template-driven page must belong to a clear topical group to avoid cannibalisation.
What I got wrong
My first mistake was treating silos as prisons. I used to block all cross-silo links with internal nofollow or by simply never linking across boundaries. Then I realised a user reading about 'on-page SEO' might also need 'technical SEO'—and Google expects those connections. Now I link contextually, even across silos, as long as the link adds value. My second error was building silos without keyword research. I once created a silo around 'best coffee machines' for a site that had no search volume for that term. The pillar page got zero organic traffic for six months. Now I always validate with tools like Ahrefs or Semrush before committing. Third, I assumed URL directories were mandatory for silos. I reorganised a client's entire site into /silo1/, /silo2/ subfolders, only to learn that flat URLs with strong internal linking work just as well. [Canonical tags](/canonical-tag/) and a consistent linking hierarchy matter more than the URL path. Finally, I underestimated the importance of maintenance. Silos need periodic [SEO audits](/seo-audit/) to check for broken links or topic drift. I now schedule a quarterly review per silo group.
Next step
Quick answers
Are SEO silos the same as topic clusters?
They are very similar. Traditional silos originally meant strict separation, but modern practice treats them as flexible topic clusters. Both use a pillar page and supporting pages with strong internal links. I use the terms interchangeably now, but I favour 'cluster' to avoid the prison mindset.
How many pages should a single silo contain?
I aim for 5–10 supporting pages per pillar page. If a silo exceeds 20 pages, I split it into sub-silos. For example, a 'running shoes' silo might have sub-silos for 'men's' and 'women's' models. The key is that every page directly supports the pillar topic.
Do I need a separate URL directory for each silo?
No. URL directories make silos visible but are not required. I have built effective silos using only internal linking patterns across a flat URL structure. A clear parent-child link hierarchy and proper breadcrumbs work just as well. Choose whichever is easier to maintain.
Can silos work for small sites with under 10 pages?
Rarely. Silos add overhead without enough content to group. I would focus on writing comprehensive pages that cover subtopics within the same article. Once you have 15–20 pages, consider siloing. Until then, a flat structure with good internal links is usually sufficient.
Sources
Primary documentation is linked directly. Anything commercial is marked nofollow.
- Google Search Central — Official guidance on site structure and internal linking.
- Ahrefs Blog — Modern critique of rigid siloing and comparison with topic clusters.
- Semrush Blog — Concise definition of silo SEO and its traditional isolated-linking model.
- Bruce Clay — Longstanding reference on silo architecture and implementation steps.
Notes from Callum Bennett.