A simple agreement replaced the seed-stage promissory note

The record

On 6 December 2013, Y Combinator announced a new seed-stage instrument called the SAFE, for Simple Agreement for Future Equity, drafted by YC partner Carolynn Levy. The announcement describes the SAFE as “essentially convertible debt without the debt”: it carries no interest rate and no maturity date, the two mechanics that had required convertible notes to be renegotiated or repaid when a priced round was slow to arrive. YC published the template for general use, intending it to become the accelerator's standard seed instrument.

What the sources establish

YC's current documents page states that YC “standardized on the post-money SAFE in 2018,” replacing the 2013 version, which measured its cap against the company's value before the SAFE money came in. The SAFE User Guide explains the difference: a post-money cap is “the maximum valuation at which your SAFE will convert into equity,” calculated after all outstanding SAFE money is added in, so an investor's ownership is fixed at investment divided by the cap, rather than diluted by other SAFEs still on the books. The guide states this design was chosen because it is simpler and “avoid[s] option pool disputes” that the pre-money version generated. A separate YC page comparing the SAFE against a convertible note states the note carries interest, “typically 2–8%,” a maturity date that “can force repayment or default,” and seniority as debt, while the SAFE ranks “junior to debt and on par with preferred stock.”

Scope and revision

These documents describe a private contract template, not a filing or a market statistic; nothing here is a reported deal size. The 2013 and 2018 versions are different instruments with different math, so a cap table built on one is not interchangeable with the other without checking which form was signed. The SAFE User Guide and documents page are living publications, retrieved 16 September 2026, and YC also publishes non-US variants for Canada, the Cayman Islands and Singapore. None of the sources report how often the SAFE is used relative to notes or priced rounds; that is a separate, measurable question the template cannot answer.

The decision in front of you

A founder or early investor reading a SAFE should first identify which version is in hand, because the pre-money and post-money forms change what a stated cap buys. This is an editorial checklist, not advice: read the document's definition of “Company Capitalization,” because that definition, not the cap headline, decides how much of the option pool and any other outstanding SAFEs count against the investor's percentage before a priced round prices them.

• Is this SAFE the pre-money or post-money form, and does the cap table already reflect that?
• What exactly is included in the document's definition of the company's capitalization at conversion?
• Does a discount, a cap, or both apply, and which one does the document say will govern?

The SAFE did not remove the negotiation from seed investing; it moved the negotiation into a small number of defined terms, which is exactly why reading those terms in the document, rather than relying on shorthand, is the whole exercise.