When you want to refer to a specific placeholder in the presentation details, which identifier...

A placeholder key is a unique identifier that is used to refer to a specific placeholder in the presentation details of an item. A placeholder key is defined in the placeholder settings item that is linked to a rendering or a sublayout. A placeholder key can also be defined in the code or markup of a component. A placeholder key can be static or dynamic. A static placeholder key has a fixed value, such as /main. A dynamic placeholder key has a variable value, such as /main-{GUID}, where {GUID} is replaced by a unique identifier at runtime. Dynamic placeholders allow multiple instances of the same component to be added to a placeholder without conflicts. References:

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