categories, tags or both?

Question

When it comes to sorting contents, I always hesitate, typically I'll have categories and tags both as reasonable options, still I wonder when to use categories and when to use tags or even, when to use both? Categories looks simple and simpler to implement and tags provide much more flexibility but often appears to be too complex and affects usability. Think about del.icio.us for example, looking for content in thousands of tags is not an interesting thing. To this point I bet categories are actually more practical. Because like delicious what's really working is the hottest tags which I think, conceptually, are 'categories'.

I saw wordpress is using a general scheme to handle this. It implements a general taxonomy to deal with categories and tags in the same manner. It makes the implementation a bit more complicated tho.

I'd like to hear other people say about this. Thanks.

Answer 1

It totally depends on your application. Look at SO with its massive data base (almost half a million questions), all handled through tags - works fine. But then, the number of tags is carefully controlled, and the user base knows its buzzwords and is extremely used to navigating through big amounts of information.

In a yellow pages directory, that non-technical people use who don't browse there every day and a structure is essential for carefully navigating towards the sought after branch or business, tags could be counter-productive and the application far better off with categories. Really depends on what you want to do. Care to elaborate?

Answer 2

I'm not sure there's a single, correct answer to this.

Tags are a paradigm that imply overlap, while categories imply no overlap.

Categories (either as a flat list or hierarchy) have historically been most useful for organizing dozens or hundreds of entities.

Tags have historically handled hundreds of thousands of entities better.

Neither is more correct as a general rule.

Answer 3

I think "categories", generally speaking, are: (1) pre-defined and centrally managed and (2) hierarchical; whereas tags can be added dynamically by any CMS author and use a flat namespace. I think for many applications, there is a tension between "taxonomy" and "folksonomy" - which basically comes down to control. But I think most CMS's can benefit from both - allowing for a formal taxonomy structure which is managed, and for a less formal tag function, which all authors contribute to. Content can then be browsed by category or searched by tag.

Answer 4

Categories are very static, so they are great if you know the content. For example, news portals have always used categories for Local, Domestic, Foreign, Sports, Finance etc. news.

Tags are better for unstructured content, for example blogs.

Usually I see the pattern that you have "few categories with many items in each" or "many many tags, sometimes with only 1 or 2 items in them". I found tagging much more useful for my blog as I really don't know what types of posts I'll post in the next 12 months, whereas I would find it weird to have them on a news portal (even though some news border multiple categories), especially since the creators know what types of news they'll post and any change would be a big "Explore the new redesign!" change.

Tags are lightweight: They can be created and used without any friction, but you couldn't really put them into a structured navigation, with the tag cloud being a (IMHO bad) attempt of structuring them. Categories are rather heavyweight: They are usually tied in closely with the overall layout/navigation/design of the site and creating a new category usually means making some other changes.

Of course, that varies from Application to Application, and sometimes there is no clear distinction. After all, Categories and Tags are technically the same: A list of strings/metadata applied to an entity.

Answer 5

I often use tags as a replacement for very specific or transitory sub-categories that can't be easily defined ahead of time.

As an example, I might set up news CMS with a "Politics" category, with sub-categories of "Senate", "House", "White House", "Supreme Court", etc. My tags would be things like "healthcare reform", "Roe vs. Wade", "Ruth Bader Ginsburg", "filibuster", etc.

Answer 6

Good question. Category are conservative and hierachy-based, tags are less structured and anarchy ;)

Maybe try to ask or think like your audience (customers/users), would they prefer a more category based browsing (hierachies) or an overlap tag-based search? It is always good "how" your audience thinks.

You said your target is a CMS, what kind of domain is it covering (news, internal enterprise, techie-stuff)?

I think stackoverflow team decided well to use tags. Loads of question just can't be 100% put to one category.

Still with both approaches one has to find a good balance: A million of tags or a 20-level deep category-tree will end in hell.