The counter-set property gives authors direct, explicit control over named counters by assigning one or more counters a specific baseline value on a particular element. When you apply it, you establish or change the stored value for the named counter(s) at that point in the document tree; subsequent descendants will see and build on that value unless it is changed again further down the tree. This makes counter-set ideal for situations where you need deterministic numbering that doesn't depend purely on automatic increments — for example, when resuming numbering after an interruption or when establishing a starting point for a custom sequence.

Unlike automatic adjustments, counter-set is used to place counters at an exact value rather than simply incrementing or resetting them to a default state. It complements properties that manage counters in other ways: see counter-reset for declaring fresh counters or resetting them to their initial condition, and counter-increment for advancing a counter as the flow progresses. Together these controls let you mix automatic sequencing with manual overrides — for instance, you can establish a starting point with counter-set, let the document advance counters with increments, and occasionally reset with explicit resets.

Counters set by counter-set are typically surfaced to users via generated content in pseudo-elements or other content-generation mechanisms. To render the counter value into the page layout you usually pair the counter with mechanisms that insert generated text into the document flow; see content for how generated content picks up and displays counter values. Because the counter’s value is part of the element tree state rather than plain inheritance, changing it at one element creates a new baseline for that element’s subtree without globally affecting unrelated branches.

Practical uses include nonstandard numbering schemes (such as combining multiple counters for chapter/section/subsection formats), manual control over list numbering when combining lists from different sources, and resuming or synchronizing numbering across document fragments or paginated sections. Keep in mind that stacking multiple applications of counter-related properties allows fine-grained control — you can set explicit values where needed, allow automatic increments elsewhere, and reset contexts when a new structural boundary is required.