A lockup period is the 90 to 180 day window after an IPO during which insiders are contractually barred from selling or transferring their shares. Also called an IPO lockup, the restriction binds founders, employees, pre-IPO investors, and certain other affiliated parties, including from hedging their shares. It is designed to prevent a post-IPO supply shock that would tank the newly-public stock and to give the market time to absorb the float available from the offering itself. It is one of the most important structural features of a traditional IPO and one of the things direct listings deliberately abandon.
The standard structure: the underwriters require all insiders to sign lockup agreements as a condition of the IPO, with...