A SAFE is a Y Combinator-designed financing instrument that converts into equity at a future priced round, with no maturity date and no interest.
Plain definition
A SAFE, short for Simple Agreement for Future Equity, is a financing instrument designed by Y Combinator in 2013 to replace convertible notes for early-stage rounds. It is not debt, has no maturity date, accrues no interest, and converts into equity at a future qualified financing or liquidity event.
Like a convertible note, a SAFE typically uses a valuation cap, a discount, or both to decide the conversion price at the next round. Unlike a note, a SAFE cannot come due. The investor is committing capital with no claim to repayment, only the right to convert at the agreed terms when a priced round happens.
A SAFE is the cleaner instrument on paper, but the conversion stack still produces the same dilution math when multiple SAFEs convert at a priced round.
What goes wrong
Three rounds of SAFEs at different caps and different discounts all convert at the next priced round. The conversion math compounds the dilution and the founder reviews the post-conversion cap table for the first time at the priced-round close.
Y Combinator updated the standard SAFE in 2018 to a post-money structure. Post-money SAFEs lock in the investor's percentage as a fraction of post-money valuation, regardless of how many other SAFEs convert in the same round. Founders signing the new template without modeling the post-money math get more dilution than they expected.
A SAFE with a $10M cap signals to future investors that the founder believed the company was worth $10M when the SAFE was signed. The next priced round often anchors near the cap, even when the company has grown beyond it. The cap becomes a ceiling, not a floor.
Most-favored-nation language in early SAFEs grants the early investor any better terms given to a later SAFE investor. A second SAFE round at a lower cap pulls the first investors down with it. Founders sometimes sign the second SAFE without re-reading the first.
Founder questions
Bigger picture
Convertible notes are the older cousin of the SAFE. The SAFE removed maturity, interest, and debt mechanics, but inherited the cap and discount conversion logic.
Related structure Liquidation PreferenceSAFEs typically convert into preferred stock at the priced round. The preference attached to that stock decides what conversion is actually worth at exit.
Related structure Capital Raise That Cost ControlThe case pattern of early instruments compounding into a priced round inside a real founder-led company.
Related reading
How the choice of capital changes which protections sit on top of the cap table.
Related readingTiming decisions that shape what a SAFE round actually costs at conversion.
Related readingWhy capital structure decisions made early decide what later rounds and exits actually pay.
Bring the SAFEs, their caps and discounts, and the proposed priced round terms.