It is OK to Say It is OK to Say It is OK to Say It is OK to Say “CSS Variables” “CSS Variables” “CSS Variables” “CSS Variables” Instead of (or Alongside) Instead of (or Alongside) Instead of (or Alongside) Instead of (or Alongside) “Custom Properties” “Custom Properties” “Custom Properties” “Custom Properties”
TPAC 2025 just ended, and I am positively tired. Attending it remotely, my sleep schedule is chaotic right now. I have many ideas for CSS-related posts in my list of ideas for November, but almost all of them require at least some amount of research and crafting demos.
Well! I found one note that I wanted to expand on, and which sounds tiny enough to be able to finish it in my altered state.
Let me repeat the title of this post: it is OK to say “CSS Variables” instead of (or Alongside) “Custom Properties”.
I won’t say that this is something contentious, but it was always mostly a thing where I always stumbled a bit before continuing using the terminology.
The official name of the corresponding CSS module is “CSS Custom Properties for Cascading Variables”. It’s URL’s slug is css-variables .
They are variables. More specifically: cascading variables. They change with the cascade: when different rules match, values can be overridden and change.
We can have animations that involve custom properties, or custom properties with values based on the viewport, containers, or something else — dynamic, responsive values that can vary for multitudes of reasons.
They are also custom properties, and even the more property-like when using @property . They can also be explicitly typed, while the rest of CSS is often typed implicitly. But — typed, unlike some other “programming languages”.
Ah, yes, CSS (and HTML) are programming languages, and anyone thinking otherwise is wrong. The best programming languages, according to me, by the way.