The SAFE, fully explained.

SAFE stands for Simple Agreement for Future Equity. It is a contract under which an investor wires money now in exchange for the right to receive shares later. Y Combinator published it in 2013 to replace the convertible note for the earliest rounds, and it has since become the default: by Carta’s data, close to nine in ten pre-seed rounds use one.

The reason for its popularity is also the reason it is so easy to misjudge. A SAFE is not debt: no interest accrues, there is no maturity date, and nothing ever has to be repaid. It is also not stock: the investor owns no shares, has no vote, and sits on no cap table, at least not yet. It is a third thing: a standing right to equity that lies dormant until a trigger fires.

Because it is neither debt nor equity, a SAFE skips the two hardest things about early fundraising: agreeing a valuation today, and papering a full preferred-stock round. That is the whole pitch: speed and standardization. The table below places the SAFE between the convertible note it was built to replace and the priced round it postpones.

For all its reputation for complexity, a SAFE has only a handful of moving parts. Two are economic terms inside the document; two are rights usually granted in a short side letter. In the overwhelming majority of rounds, the valuation cap is the only number actually negotiated. Everything else is left at the standard setting.

The single most important thing to know about any SAFE is which kind it is. In 2018, YC re-engineered the instrument around a post-money valuation cap. The change sounds technical but it fixed the original’s biggest flaw: under the old pre-money SAFE you could not say, on the day you signed, exactly how much of the company you had sold. Under the post-money SAFE you can, with nothing more than addition and division.

Start from how much of the company you want to sell. If you are targeting a $1 million raise for 15% ownership, the cap falls straight out of the arithmetic. Once the cap is set, every investor’s stake is just their check divided by that cap, and several caps simply add up.

The implied percentage is a promise; conversion is where it becomes shares. A SAFE converts on an Equity Financing: the company’s first sale of preferred stock. Walk through the mechanics, using the cleanest teaching case: a SAFE that carries both a cap and a discount, so you can see which one wins.

Conversion is easiest to grasp on a full example. Take a company that raised $1M across two SAFEs (Investor A, $200K at a $4M cap; Investor B, $800K at an $8M cap), then closed a $5M Series A led by Investor C for 20%. The cap table below shows the moment before the round, with each SAFE at its implied (as-converted) stake, and the moment after it converts: founders stay in control, the SAFE holders land near their implied stakes, shaved down only by the new option pool.

The same instrument behaves very differently depending on which event arrives first, and at what valuation. Take Investor B’s $800K SAFE at an $8M cap (a 10% implied stake) and follow it into each possible future. This branch is the heart of the SAFE: the investor’s share, in percent or in dollars, depends entirely on what happens to the company.

Most SAFE negotiation happens not in the form itself but in the side letter. Sophisticated investors ask for a standard set of rights; the line between “market” and “aggressive” is well established. Founders should grant the first column freely and resist the second; investors should expect the same.

For the earliest rounds, the SAFE is hard to beat: it is fast, cheap, standardized, and, in its post-money form, transparent about exactly what is being sold. Its rough edges are real but mostly the price of that standardization, and each is fixable in a side letter. The honest summary is that the SAFE is an excellent default that you should still take the time to understand. Here is when to reach for it, and when to reach for something else.

Disclaimer

This longread is for informational purposes only and is not legal, tax or investment advice. The figures are drawn from Y Combinator’s illustrative examples and public market data; actual outcomes depend on the executed documents, the company’s capitalization and the terms of each financing. The standard YC SAFE is drafted for US Delaware C-corporations; other jurisdictions require modified forms. SAFEs and their conversion can produce more dilution than estimated where a round prices near the cap. For advice on a specific financing, please contact Buzko Krasnov.