The instrument you sign decides when your dilution is fixed

The record

Y Combinator's own SAFE page, as retrieved on 16 September 2026, describes the instrument's origin and current form: a Simple Agreement for Future Equity created at Y Combinator by Carolynn Levy in 2013, used to raise more than $15 billion for YC portfolio companies, standardized in post-money form since 2018. The page's definitions set out the mechanics: a valuation cap is the highest valuation at which the SAFE converts, a discount gives a lower price than the next priced round, and on a post-money SAFE, ownership sold equals investment divided by the valuation cap, illustrated with $500,000 on a $6.7 million cap selling about 7.5% and $1,000,000 on the same cap selling about 15%.

What the sources establish

Y Combinator's separate guide to seed fundraising states why the SAFE displaced convertible debt at YC in the first place: it strips out the interest rate, maturity date, and repayment obligation that make a note a debt instrument, leaving only amount, cap, and discount as negotiable terms. The same guide is direct about the alternative: setting a priced equity round is 'always more complicated, expensive, and time consuming than a safe or convertible note,' which the guide gives as the reason priced rounds are uncommon at seed stage. Cooley GO's Series Seed document package shows what that added complexity consists of concretely: a priced round under its template requires a term sheet, an amended and restated certificate of incorporation, a preferred stock investment agreement, an investor suitability questionnaire, and a board consent, five interlocking documents in place of a SAFE's single agreement.

Scope and revision

The two instruments answer a different question about timing. A SAFE defers exactly how much ownership was sold until a future priced round sets a per-share price, which makes it fast to sign but also makes a stack of SAFEs with different caps and discounts hard to model until conversion. A priced round fixes ownership, valuation, and share price at signing, at the cost of the negotiation and documentation Cooley's package enumerates. Neither document set states which is better for a given company; both are described by their publishers as standard forms, not advice about when to use them.

The decision in front of you

As editorial guidance beyond what these documents state, a founder choosing between them is trading speed and deferred pricing against certainty and cost: a SAFE suits a fast close where the eventual valuation is genuinely unclear, while a priced round suits a company and investor who can agree on a valuation now and want the ownership question closed immediately.

• How many outstanding SAFEs or notes, at what caps and discounts, will convert at the next priced round?
• Does the deal's timeline and size justify a priced round's added legal cost and documents?
• Is a post-money or pre-money cap being used, and is that difference reflected in the ownership math?

Both instruments are published as standard, founder-tested forms; the choice between them is a scheduling and certainty decision, not a legal judgment this trace can make for any specific company.