SAFE
A SAFE (Simple Agreement for Future Equity) is a seed-stage financing instrument in which an investor provides capital to a startup today in exchange for the right to receive equity at a later date, when a defined triggering event occurs — typically a priced funding round (Series A), an acquisition, or an IPO.12
Unlike a loan, a SAFE carries no interest and has no maturity date. Unlike a priced equity round, it requires no agreed valuation at the time of investment. This makes it faster, cheaper, and simpler than both alternatives — a SAFE can be signed in days with minimal legal fees.3
Origin
The SAFE was created by Y Combinator managing director Carolynn Levy in 2013 and announced in a YC blog post titled "Announcing the Safe, a Replacement for Convertible Notes."13 The instrument was designed to solve a specific problem: convertible notes — the dominant pre-Series A instrument at the time — were structured as debt, accruing interest, carrying maturity dates, and creating legal pressure to either convert or repay. For very early companies raising small rounds, this complexity was unnecessary overhead.1
YC released the SAFE as an open document, free for anyone to use, and it rapidly became the industry standard for seed financing in the US.4
How a SAFE converts
When the triggering event occurs (usually a priced Series A), the SAFE converts to equity. The conversion price is determined by whichever mechanism gives the investor a better deal:32
- Valuation cap — a ceiling on the price at which the SAFE converts. If the company raises at a $20M valuation but the SAFE has a $10M cap, the investor's shares are priced as if the company is worth $10M — giving them roughly 2x more shares than a new investor.
- Discount rate — a percentage reduction off the Series A price. A 20% discount means the SAFE converts at 80 cents on the dollar vs. new investors.
- MFN clause (Most Favored Nation) — no cap or discount, but the investor gets the right to adopt the terms of any subsequent SAFE that is more favorable.
As of 2024–25, the dominant SAFE uses a valuation cap with no discount. Uncapped MFN SAFEs have become rare.4
Pre-money vs. post-money SAFE
The original 2013 SAFE was a pre-money SAFE: the cap was applied to the pre-money valuation of the conversion round. This created ambiguity about actual ownership percentages when multiple SAFEs were outstanding, because each SAFE diluted the others.4
In 2018, YC released an updated post-money SAFE, which applies the cap to the company's post-money valuation at conversion. This gives both founders and investors precise knowledge of the investor's ownership percentage at the moment of signing — not at some uncertain future conversion event.4
| Version | Cap applied to | Ownership clarity at signing |
|---|---|---|
| Pre-money SAFE (2013) | Pre-money valuation at Series A | Uncertain |
| Post-money SAFE (2018) | Post-money of the SAFE round | Known |
SAFE vs. convertible note
| Feature | SAFE | Convertible note |
|---|---|---|
| Legal structure | Not debt | Debt instrument |
| Interest | None | Accrues (typically 4–8% annually) |
| Maturity date | None | Typically 12–24 months |
| Investor protection at liquidation | Weaker | Stronger (debt seniority) |
| Complexity and legal cost | Low | Medium |
SAFEs are generally more founder-friendly. Convertible notes remain more common when investors want debt seniority, or in jurisdictions where SAFEs are less legally tested.3
YC's current deal
YC's standard investment consists of two SAFEs: a $125,000 post-money SAFE at a 7% equity cap, and a $375,000 uncapped SAFE with an MFN clause — totaling $500,000.5 The split structure lets YC maintain a predictable ownership stake while giving companies flexibility on the uncapped portion.
The SAFE is also the instrument used in YC's term sheet-free investment model — founders receive funding with no board seats, no protective provisions, and no governance strings attached at the seed stage.