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Creating expressions


    All of your work adding, editing, and writing expressions occurs in the Timeline window. When you add an expression to a layer property, a default expression appears in a text field under the property. Use this field to type new expressions or edit expression variables. Some expressions rely on the names of layers in your project; if you change the name of a layer that is involved in an expression, the expression will not work.

To create an expression:

  1. Select a property in the Timeline window and do one of the following:
    • Choose Animation > Add Expression.
    • Alt-click (Windows) or Option-click (Mac OS) the property's stopwatch icon.

    Note: After Effects automatically fills the expression field with a default expression that copies the fixed value of the property, or the value of the keyframes, if any.

  2. Create the expression by doing one of the following:
  3. Click outside of the expression field or press Enter on the numeric keypad to activate the expression.
  4. Note: If an expression cannot be processed, After Effects displays a message explaining the error and automatically disables the expression. A yellow warning icon (Many effects support 16 bits per channel. If an effect supports only 8 bits, and your project is set to 16 bits, After Effects displays a warning icon) appears next to the expression; click the warning icon to view the error message again.

    Illustration with these callouts: A. On/Off switch B. Graph overlay icon C. Pick whip D. Language elements menu E. Expression field
    A. On/Off switch B. Graph overlay icon C. Pick whip D. Language elements menu E. Expression field

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