# 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 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.