Taxonomy design

Taxonomies decide what appears together. A news listing filtered by "Health", a product page tagged "Waterproof", a search filter for "Brisbane": each depends on someone applying the right label to the right item, every time. When a taxonomy has no rules, labels multiply. One editor writes "Covid-19", another writes "COVID", a third writes "Coronavirus", and the listing for any one of them shows only a third of the relevant content.

What taxonomy design covers

Vocabularies. Which separate lists you need. A site might have topics, content types, audiences and locations, each answering a different question about an item. Mixing them in one tag list is the source of a lot of confusion.

Terms. The labels in each vocabulary, written in your audiences' words, with a short definition for any term that could be read two ways.

Structure. Whether a vocabulary is flat or has parent and child terms, and how deep it may go.

Rules. How many terms of each kind an item may carry, which are required, and who may add a new term. Rules matter more than the first list of terms, because the list will change and the rules keep it in shape.

Use in the interface. Where each vocabulary appears: in navigation, filters, related-content blocks, search facets or only behind the scenes.

Taxonomy, filters and search engines

Filters built from a taxonomy can create very large numbers of URLs. Google's guidance on faceted navigation warns that such filters can produce very large, even effectively infinite, sets of URLs, which can lead to overcrawling. Its advice includes using the standard "&" separator for parameters, keeping filter order consistent and returning a 404 status when a filter combination has no results. We include these points in the developer notes so your filters help people without flooding search engines with near-identical pages.

How the work runs

1. Inventory. Export the current categories, tags and filter values with usage counts.
2. Analyse. Find duplicates, near-duplicates, unused terms and terms that do two jobs at once.
3. Research the words. Site search logs, support enquiries and, where useful, a card sort. Digital NSW describes card sorting as participants "organising topics into categories that make sense to them", which is exactly what a taxonomy needs to reflect.
4. Draft. Vocabularies, terms, definitions and rules.
5. Map. An old-to-new mapping for every existing term, so content can be re-tagged by script where your system allows.
6. Govern. A short policy on who maintains each vocabulary and how new terms are requested.

What you receive

• A taxonomy workbook: one tab per vocabulary, with terms, definitions, parents and status.
• A rules sheet that editors can follow without training.
• An old-to-new term mapping for migration.
• Interface notes covering navigation, filters and related-content blocks.
• A governance note with a simple request process for new terms.

Working with your content system

Content systems differ in how they store and display taxonomies. Some treat categories as a hierarchy and tags as a flat list; some let you define any number of vocabularies; some limit you to one. We write the taxonomy in plain language first, then add notes on how it maps to your system, including which vocabularies become fields, which drive URLs and which stay hidden. Where your system cannot support part of the plan, the notes describe a workable alternative.

Signs you need taxonomy work

• The tag list is longer than anyone can scroll through.
• Listings and filters show some relevant items but miss others.
• Two terms mean the same thing, or one term means two things.
• Editors add a new tag for every article because they cannot find an existing one.
• Filters produce pages with no results.

A worked illustration

Try it on a sample

The free taxonomy planner lets you paste a few items with their categories and tags, then points out missing categories, unused tags and labels that look like duplicates. It is a good way to see the size of the problem before you ask for help.

Questions about this topic

What is the difference between a category and a tag?

We use category for a broad grouping where each item has one primary home, and tag for a descriptive label that can apply to items in different categories. Content systems handle the two differently, so we document how each vocabulary is meant to be used on yours.

Can you clean up an existing tag list?

Yes. We export the current tags, merge duplicates and near-duplicates, retire tags used once or not at all, and give you a mapping from old tags to new ones so the change can be scripted.

Will a new taxonomy break our filters?

It can if old values disappear without a mapping. The plan includes a mapping table and notes for developers so filters, listings and saved links keep working.

Sources checked 4 November 2026 for taxonomy design

1. Card sorting, Digital NSW
2. Card sorting method, 18Fsecondary
3. Faceted navigation, Google