What rebirth does
Rebirth resets your cash in exchange for permanent multipliers to Luck and Cash. The rebirth control is reported to be the circular-arrow icon between Shop and Index on the left side of the screen.
The threshold conflict
Sportskeeda reports a first rebirth at 50,000 Cash. RoboLibrary and a Bloxodes in-game panel screenshot report $500M, with the multiplier moving from 2x to 2.5x for both Luck and Cash. These cannot both describe the same current build, and no source resolves the difference, so this wiki shows both and treats the in-game panel as the only reliable check.
Spend your surplus before you rebirth
Three sources agree that cash resets and that anything above the threshold is forfeited. Because dice and upgrades are reported to survive a rebirth, the repeated community advice is to spend surplus cash on those before pressing the button.
What is reported to survive
Units, gems, trait rerolls, dice and upgrades are all reported to carry through a rebirth. Bloxodes describes this as current reported behaviour and tells readers to confirm in the in-game confirmation panel, so treat it as community reporting rather than a documented guarantee.
Rebirth two and beyond
Only the first rebirth step appears anywhere in the public record. Sources say the requirements and multipliers increase but none publishes the ladder. This wiki does not estimate the later steps, and it does not offer a rebirth timer, because no source publishes a cash-per-second rate that a timer would need.