Everyone must now act like a startup due to the sudden changes caused by the pandemic. To succeed during a crisis, companies should 1) identify hypotheses about how the world currently works and may work in the future, 2) test these hypotheses and accompanying tactics to understand what is known, and 3) adapt tactics that work and be ruthless about abandoning what no longer works, as the world is now different and past successes may not translate. Acting like a startup by pursuing this process of trial, learning, and change will help companies thrive during uncertain times.