Definition
What is vesting acceleration?
Acceleration speeds up vesting when a specific event happens, usually an acquisition. Single-trigger acceleration vests shares on the sale itself; double-trigger also requires the person to be let go after the sale.
Double-trigger acceleration is the more common founder-friendly compromise, because acquirers are often reluctant to buy a company whose founders become fully vested — and free to leave — on day one.
Acceleration terms are set in the founder stock agreements or the equity plan; have a lawyer review them.
General information, not legal, tax or investment advice.