Layer opacity determines how transparent or opaque a layer is. A layer with 0% opacity is completely transparent —and invisible— while a layer with 100% opacity is completely opaque. As you lower a layer’s opacity value it’ll reveal and blend with any content behind it.
There are two modes of layer opacity: Default and Progressive alpha. Both are available under Appearance in the Inspector. You can change the opacity of any layer: shape, text, frames, groups or symbol instances.
Default opacity
New layers have a default opacity of 100% . To change default opacity, select one or more layers, then drag the slider in the Inspector — or enter a value from 1 to 100 in the input field.
To change the default opacity, click and drag the slider or enter a value from 1 to 100 in the input field.
Progressive alpha
Progressive alpha opacity has start and end stops, similar to gradients. The start is set to 0% (fully transparent) and the end is set to 100% (fully opaque). Transparency fades gradually between the stops, which you can move freely across the layer, or add more stops if you need them.
To set progressive alpha opacity, select one or more layers and click on its icon on the right side of the Opacity section. From here, you can adjust the individual stops on your layer. To edit a layer’s with progressive alpha, select the layer and click on the sliders icon
in the Inspector to display the stops on the canvas.
To change opacity in alpha mode, click on the circle on the right side of the Opacity section
Note: You can also separately adjust the opacity of Fills and the alpha value of color you apply on other layer properties like Borders, Shadows, Inner Shadows, Tints or Text.