A co-sale (also called a tag-along right) is a right that lets certain shareholders participate in a sale of shares by another shareholder(often founders or a major holder) to a third party.
Typically, if the major shareholder proposes to sell their shares, the co-sale holders can “tag along” and sell a proportional number of their own shares on the same terms and price to that buyer. This helps protect minority investors from being left behind if control or a large position is sold.
