Expression errors

If an expression cannot be processed, After Effects displays a message explaining the error and automatically disables the expression. A yellow warning icon appears next to the expression; click the warning icon to view the error message again.

To show expressions that have errors, select one or more layers, right-click (Windows) or Control-click (Mac OS) a selected layer in the Timeline panel, and choose Reveal Expression Errors from the context menu.

Some expressions rely on the names of layers or properties in your project; if you change the name of a layer or property that is involved in an expression, After Effects attempts to update the expression to use the new name. However, in some complex cases, After Effects is unable to automatically update the expression, in which case the expression may produce an error message, and you must update the expression yourself.

Important: If you are running After Effects in a language other than the one for which an expression was written, or if you have changed the names of items (such as layers, effects, or other property groups), then the expression may not work until you modify the expression to use the new names or the strings that match the language in which you are running After Effects. Because the examples in this document were created for the default state of After Effects running in English, some examples in this document will not work without such modification.

Note: The arguments for some After Effects effects have changed from the arguments in previous versions. If you have existing expressions that use argument index references rather than argument names, you may need to update the expressions to use argument names.

Precomposing multiple layers can also cause expressions that refer to a property of one of the layers to produce an error, requiring you to update these expressions to refer to the layer within the new composition. This is especially a concern with expressions that use thisComp instead of referring to a composition by its name. (See About precomposing and nesting.)

Jeff Almasol provides a script on his redefinery website with which you can replace instances of thisComp with explicit references to a composition’s name.