FTLN meaning in Shakespeare's Hamlet

I'm looking at Shakespeare's Hamlet. the lines start with a FTLN reference number.

(FTLN 1762) [64] To be or not to be—that is the question:

What does FTLN stand for? Is this a standard Shakespeare reference of some kind?

Thanks so much!

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Folger Through Line Number. It’s a coding scheme used by Folger Digital Texts.