Difference between : and :: in CSS [duplicate]

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• Should I use single or double colon notation for pseudo-elements? 4 answers

Hi just want to clear up my mind to use colon / pseudo class in css.

If I use

div:before {
    // some css styles
}

OR

div::before {
    // some css styles
}

Both works same. So what is the difference between single colon : or double colon ::?

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