# Expression Builder Features

Expression Builder has some built-in features that are intended to help you construct your expressions.

- Syntax highlighting: To find errors easier, non-existing functions, identifiers and tags are highlighted with a red background (the error message is collapsed by default).

  The text editor also uses the same syntax highlight color scheme as the Script Editor. The text editor highlights the following language elements:

  - Operators
  - Constant values
  - String literals
  - Tag references
  - Function names

  - Comments

- Auto-completion: The text editor provides an auto-completion function with IntelliSense-like features. Pressing Ctrl+Shift+Space or Ctrl+Space will search for relevant functions, constants, and tags.

- Creating tags on-the-fly: Expression Builder does not allow you to save the expression if it is invalid. There is, however, one exception to this behavior; you can save the expression with invalid tag names. In this case, the (yet) nonexistent Tag is highlighted and you can create it later in Tag Manager.