01What a SAFE Is
SAFE stands for Simple Agreement for Future Equity. The instrument was created by the accelerator Y Combinator in late 2013 to simplify the earliest rounds. Since then it has become the main way to bring the first money into a startup.
The idea in one sentence: an investor sends money to the company now and, in return, gets the right to receive shares later — when the company raises a proper priced round (usually Series A). The easiest way to think of a SAFE is as a prepayment: the money goes in today, and the "goods" — the shares — are delivered once there is a clear price for them.
02How a SAFE Differs from a Loan
A SAFE is often confused with a convertible note, but they are different. A SAFE has no interest and no repayment date — it is not debt. The company owes nothing back: if a round never happens, the money simply stays in the company.
The investor takes a risk — they come in earliest, when almost nothing about the company is clear yet. In exchange for that risk, they convert on better terms than the people who join at the future round: more shares for the same money. Exactly how much better is set by two parameters: the valuation cap and the discount.
03How the Valuation Cap Works
The valuation cap (often just "cap") is the maximum company valuation at which the investor's money turns into shares. The point is easiest to show with numbers.
04How the Discount Works
The discount is a reduction on the share price at the future round — usually 10–20%. If new investors in the round buy a share for $1, a SAFE holder with a 20% discount buys it for $0.80 — and gets more shares for the same money.
The cap and the discount are two alternatives: a SAFE usually uses one or the other. Which is better depends on the price of the next round. If the round is priced above the cap, the cap wins: it credits the investor a lower valuation than new investors pay. If the round comes in below the cap, the cap does not bite, and the discount gives more. The two can be combined in one document, though that is rare.
05Pre-money vs Post-money — the Difference
This is about the moment at which the valuation is measured. The same "cap of $5M" gives the investor a different stake in the two versions — which is why they must not be confused.
- Post-money (the modern standard) — the cap is measured after all the money raised through SAFEs is counted. The main advantage: the investor's stake is known immediately and precisely. It equals: investment ÷ cap. $100,000 at a $5M cap = exactly 2%.
- Pre-money (the older version) — the cap is measured before this money comes in. The final stake also depends on how much the company raises through other SAFEs, so it is harder to predict in advance. The same $100,000 at a $5M cap gives roughly 1.96% — and that stake shrinks with every new SAFE.
This predictability is exactly why the post-money version became the standard. To avoid doing the math in your head, here is a calculator: it shows the investor's stake for any combination of parameters.
06SAFE Calculator
This is a simplified estimate: it does not account for the option pool, later rounds, or their dilution. The actual stake is calculated from the documents of the specific deal.
07Why a SAFE Does Not Work with an LLC
A SAFE converts into shares — and only a corporation has shares. An LLC has no shares: it has membership interests, to which a standard SAFE does not apply. That is why companies raising through SAFEs are set up as corporations.
08Common Mistakes
- Not knowing whether your SAFE is pre-money or post-money. These are two different versions. With the same "$5M cap," the investor ends up with a different stake — and you can hand over more of the company than you meant to. Always check which version it is.
- Losing track of signed SAFEs. Every SAFE is a piece of the company you have already promised; it just becomes shares later. Keep them loosely, and before the round it turns out more was given away than you thought.
- Taking dozens of small checks on SAFEs. Large (lead) investors dislike a crowded cap table made of many small investors: it complicates and slows down the next round. A few strong checks are often better than a crowd of tiny ones.
- Giving away too large a stake through SAFEs. Every SAFE reduces your stake as a founder. If a lot has been given away in total, by the time of the big round you may have noticeably less than you counted on.
09Frequently Asked Questions
- Y Combinator — Safe Financing Documents (official templates and explanation)
- Y Combinator — Safe User Guide (PDF with sample conversion calculations)
This material is for informational purposes and is not legal or tax advice.
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