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English definition of “opt-in”

opt-in

noun [C or U] /ˈɒpt.ɪn/ US  /ˈɑːpt-/
the fact of choosing to take part in an activity, arrangement, etc. rather than being forced to take part: The government operates an opt-in rather than an opt-out system, which means that permission must be sought on a case-by-case basis.
(Definition of opt-in noun from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)

Definitions of “opt-in” in other dictionaries

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