I have 20 multiple images in different layers withon a Photoshop file. I want to apply one clipping mask for all the layers. I grouped all layers and tried but the clipping mask option is disabled. How can I apply one clipping mask to multiple layers?
Highlight all the layers and choose "Convert To Smart Object" from the Layer Panel Menu.
Apply your clipping mask to the resulting Smart Object.
To address the comment below:
If you wish to retain existing smart objects, then merely Group all the layers you wish to mask in the Layers Panel, and apply the mask to the Group.
In Photoshop CS6, select all the layers you wish to be clipped, click on the Layers panel flyout menu and choose "Create Clipping Mask".
Make sure the masking layer is immediately below the bottom-most layer to be masked (and not selected).
Alternatively, if Layer Masks are acceptable, you can group the Layers and add a Layer Mask to the layer group.