counter()

The counter() CSS function returns a string representing the current value of the named counter, if there is one. It is generally used in the content property of pseudo-elements, but can theoretically be used anywhere a <string> value is supported.

/* Simple usage */
counter(countername);

/* changing the counter display */
counter(countername, upper-roman)

A counter has no visible effect by itself. The counter() function (and counters() function) is what makes it useful by returning developer defined strings (or images).

<custom-ident>

A name identifying the counter, which is the same case-sensitive name used for the counter-reset and counter-increment. The name cannot start with two dashes and can't be none, unset, initial, or inherit.

<counter-style>

A <list-style-type> name, <@counter-style> name or symbols() function, where a counter style name is a numeric, alphabetic, or symbolic simple predefined counter style, a complex longhand east Asian or Ethiopic predefined counter style, or other predefined counter style. If omitted, the counter-style defaults to decimal.

counter( <counter-name>, <counter-style>? )
where 
<counter-name> = <custom-ident>
<counter-style> = <counter-style-name> | symbols()
where 
<counter-style-name> = <custom-ident>

HTML

<ol>
  <li></li>
  <li></li>
  <li></li>
</ol>

CSS

ol {
  counter-reset: listCounter;
}
li {
  counter-increment: listCounter;
}
li::after {
  content: "[" counter(listCounter) "] == ["
               counter(listCounter, upper-roman) "]";
}

Result

HTML

<ol>
  <li></li>
  <li></li>
  <li></li>
</ol>

CSS

ol {
  counter-reset: count;
}
li {
  counter-increment: count;
}
li::after {
  content: "[" counter(count, decimal-leading-zero) "] == ["
               counter(count, lower-alpha) "]";
}

Result

• Using CSS Counters
• counter-reset
• counter-set
• counter-increment
• @counter-style
• CSS counters() function