# Document.compatMode

Indicates whether the document is rendered in Quirks mode or Standards mode.

## Syntax

```mode = document.compatMode
```

## Values

• `"BackCompat"` if the document is in quirks mode;
• `"CSS1Compat"` if the document is in no-quirks (also known as "standards") mode or limited-quirks (also known as "almost standards") mode.
`mode`
Is an enumerated value that can be:

Note: all these modes are now defined in standards, so the older "standards" and "almost standards" names are nonsensical and no longer used in standards.

## Example

```if (document.compatMode == "BackCompat") {
// in Quirks mode
}
```

## Document Tags and Contributors

Tags:
Last updated by: teoli,