Syntax highlighting

A language id gives a code block colour. It changes nothing about the characters; it only tells the highlighter how to read them. The code is already literal, so the id is safe to add or remove at any time.

The rule

Put the id immediately after the opening fence, on the same line, with no space. Add a newline, then the code, then the closing fence. The id is a single word; do not put a colon or a second word after it. The closing fence stays bare. The newline after the id starts the first line of code; without it, the id and the first line run together.

```js
const total = price * quantity
```

const total = price * quantity

The id is not shown in the result, and it does not change the text inside the block. It only selects the colour rules. A block with a single line of code still needs both fences.

Common ids

Use the short id shown below. The table covers the languages most messages need; it is a starting point, not the full list. If your language is not here, the block still renders. Try the short id from the language’s own documentation; an id the highlighter does not know costs you colour, not the code.

No id, no colour

A fence with no id renders as plain monospace. An id the highlighter does not know does the same; the block still renders, but the text stays one colour.

```
const total = price * quantity
```

const total = price * quantity

Plain is the right choice for output that is not code: a log, an error message, or a stack trace. Colour can add noise when there is no syntax to read. A plain block is also the honest choice when the language is mixed or unknown.

Inside fences only

An id has meaning only on an opening fence. After an inline backtick, the same letters are part of the code. A fenced block also has one language from start to finish; you cannot switch halfway through. The closing fence takes no id, and a stray id there can leave the block open.

Watch out

A space between the fence and the id turns the id into the first line of the block. Keep the id against the fence: the language name belongs to the fence, not to the code. The same happens if you put the id on its own line.