Tiny Tools › URL parameter glossary › mc_eid
mc_eidMailchimp's unique recipient ID. It is tied to you specifically — it can identify which subscriber clicked. If you paste a newsletter link somewhere public, this is the one that could reveal who you are. Always safe (and wise) to strip.
Safe to remove? Yes. mc_eid is used for tracking and reporting only — deleting it does not change the page you land on. Strip it before sharing a link to keep it clean and private.