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SAFE Agreements

SAFE Agreements: What Every Startup Founder Needs to Know

By Joe Wallin,

Published on Apr 9, 2026   —   14 min read

Startup FinancingFundraisingConvertible NotesStartup LawValuation CapEquitySeries A
Business meeting representing startup fundraising

Summary

SAFEs are the dominant instrument in pre-seed and seed financing, but "simple" doesn't mean uncomplicated. Learn how SAFEs actually work, what can go wrong, and what you need to know before you sign one.

SAFE Agreements: What Every Startup Founder Needs to Know

By Joe Wallin | April 9, 2026 | ~10 min read

In This Guide

If you're raising capital as an early-stage startup, you've probably heard the term "SAFE" thrown around. Maybe an investor sent you a SAFE agreement, or your co-founders asked whether you should use one instead of a convertible note. The name suggests simplicity—Simple Agreement for Future Equity—but I'll be honest with you: SAFEs are deceptively simple on the surface and surprisingly complex when you actually live with the consequences.

I've been practicing startup law for decades, and I can tell you that SAFEs are now the dominant instrument in pre-seed and seed financing. They've largely replaced convertible notes as the go-to vehicle for early capital. And yet, I see founders make the same mistakes with SAFEs again and again: they stack too many of them, they don't model the dilution, they agree to side letters that give away the farm, and then they're shocked at their Series A closing when they realize they own far less of their company than they thought.

This post is meant to give you the lawyer's perspective on SAFEs—not just what they are, but how they actually work, what can go wrong, and what you need to know before you sign one.

What Is a SAFE, Really?

Y Combinator created the SAFE in 2013 to address a problem: early investors wanted to put money into startups, but the startups weren't ready for a priced Series A round. A priced round requires agreeing on a company valuation, which is complex when the company has minimal revenue and lots of uncertainty. So Y Combinator designed an instrument that would let investors put money in now and convert that investment into equity later, when the company either raised a priced round or hit some other triggering event.

Here's what makes a SAFE different from other instruments you might consider:

A SAFE is not debt. This is critical. Unlike a convertible note, a SAFE has no maturity date, no interest rate, and no repayment obligation. Your company doesn't owe the SAFE holder money if you never raise a Series A. There's no default event. The SAFE holder can't accelerate or demand repayment. This is fundamentally different from a convertible note, which is a loan that converts into equity at the next round.

A SAFE is not immediate equity either. The SAFE holder doesn't own shares yet. They own a right to own shares in the future, under certain conditions. Until one of those conditions is met—typically a priced Series A raise—the SAFE holder has no voting rights, no dividend rights, and no seat on your board.

So what is a SAFE? It's a warrant-like instrument. Think of it as a promise: if certain things happen (like a Series A), your current SAFE holders get to convert their investment into equity at a predetermined rate. That rate is determined by two mechanisms: the valuation cap and the discount. I'll explain both of these shortly, but the key insight is this: a SAFE gives early investors upside participation while keeping your cap table clean and simple in the early days.

Post-Money vs. Pre-Money: Understanding the Shift That Changed Everything

If you're researching SAFEs, you'll see references to "post-money" and "pre-money" SAFEs. This distinction matters far more than most founders realize, so let me explain it clearly.

When Y Combinator introduced SAFEs in 2013, they were pre-money instruments. This meant that the SAFE valuation cap didn't include the SAFE investment itself in the company's valuation. If you raised $500,000 on a pre-money cap of $5 million, the math was: investment divided by (valuation cap plus investment) times total shares. But then if you raised another $500,000 on the same pre-money cap, the second SAFE holder's conversion percentage was different from the first SAFE holder's, because the first SAFE diluted the second one. This created a cascading effect that was genuinely confusing and hard to model.

In 2018, Y Combinator switched to post-money SAFEs. Now, when you raise $500,000 on a post-money cap of $5 million, the SAFE holder's ownership percentage is crystal clear: they own $500,000 divided by $5 million, or 10 percent of the company at conversion. If you raise another $500,000 on an $8 million post-money cap, that investor gets $500,000 divided by $8 million, or 6.25 percent. You can model this on the back of a napkin.

Here's the counterintuitive part: post-money SAFEs are actually better for founders, even though many founders initially think they're worse. Yes, the investor gets a fixed ownership percentage, which might seem like it gives away more. But from a founder's perspective, post-money SAFEs are predictable. You can model your cap table. You can see exactly how much equity your SAFE holders will own at your Series A. You can plan accordingly. With pre-money SAFEs, the dilution dynamics were opaque, and founders often found themselves surprised.

Today, post-money SAFEs are the industry standard. If an investor offers you a pre-money SAFE, that's a yellow flag. It usually means they're working from old templates or they're trying to get better terms without being explicit about it.

The Valuation Cap: Your Most Important Negotiation

The valuation cap is the most important term in a SAFE, and it's the most negotiated. Here's why it matters so much.

Imagine you raise $500,000 on a SAFE with a $10 million valuation cap. Later, your company does really well, and you raise a Series A at a $50 million valuation. At that point, your SAFE holders get to convert at the cap—$10 million—rather than the Series A valuation of $50 million. This is huge. At $10 million, if each Series A share is worth $1.00, then the SAFE holder gets $500,000 worth of shares at $0.50 per share (since $500,000 divided by $10 million equals 5 percent). At the $50 million Series A valuation, they would only get $500,000 worth of shares at $1.00 per share (which is 1 percent). The valuation cap protected the early investor and diluted everyone else proportionally.

This is why the cap is the primary negotiation. From an investor's perspective, a lower cap is better—it means more shares if the company succeeds. From a founder's perspective, a higher cap is better—it means giving up less equity to early investors.

What's a reasonable cap? It depends on your stage. A pre-seed SAFE might have a cap of $3 to $8 million. A seed-stage SAFE might have a cap of $10 to $25 million. A late-seed SAFE might be $20 to $50 million or higher. These numbers change based on market conditions, your traction, and your investors' expectations. The key is to be thoughtful and not panic into an absurdly low cap just because you're desperate for capital.

Let me give you a concrete example. You're raising $250,000 on a post-money SAFE with a $6 million cap. That means your SAFE holder owns $250,000 divided by $6 million, or about 4.17 percent. When you raise your Series A at $20 million (a massive jump, but assume great progress), your SAFE holder converts at the $6 million cap, not $20 million. If the Series A has a pre-money valuation of $15 million and the post-money is $20 million, the Series A investors are paying $5 million for a percentage of the company. Your SAFE holder still owns approximately 4.17 percent, but they got that 4.17 percent at what amounts to a $6 million valuation instead of a $20 million one. That's the SAFE holder's benefit from the cap.

The danger for founders is setting the cap too low. I've seen founders who are early, desperate, and uncertain put a $3 million cap on a pre-seed SAFE. If the company succeeds and raises a Series A at $30 million, that early SAFE holder has won the lottery—they got 4 or 5 percent of the company for $200K at a $3 million valuation. Meanwhile, you as the founder are looking at your cap table and realizing you've given away massive equity to early investors on terms that didn't reflect the company's actual trajectory.

The Discount: The Alternative (or Complement) to the Cap

In addition to (or sometimes instead of) a valuation cap, SAFE agreements often include a discount. This is the percentage by which SAFE holders get to purchase their shares at a discount to the Series A price.

Let's say you have a SAFE with a 20 percent discount and no cap (or a very high cap). At your Series A, Series A investors are buying shares at $1.00. Your SAFE holders get to buy at $0.80—a 20 percent discount. If you've raised $500,000 on this SAFE, they get $500,000 divided by $0.80 per share, which is 625,000 shares. Series A investors at $1.00 per share would only get 500,000 shares for the same $500,000.

The SAFE holder gets the benefit of either the cap or the discount—whichever is better for them. So if the cap would give them a lower per-share price than the discount, they use the cap. If the discount would give them a lower per-share price than the cap, they use the discount.

Typical discounts range from 10 to 30 percent, with 20 percent being the most common in the current market. Some SAFEs have both a cap and a discount. Some have only a cap. Some have only a discount. The dynamics are nuanced, and this is another area where a lawyer can help you think through what actually makes sense for your situation.

The Hidden Complexity: MFN Clauses and the Uncapped SAFE

Y Combinator's standard deal for recent batches has included what's called an "uncapped MFN SAFE"—MFN stands for "Most Favored Nation." If you're taking Y Combinator funding, you're likely dealing with this.

Here's what an uncapped MFN SAFE means: the investor gets a most-favored-nation clause, which means if you later issue a SAFE with better terms, this investor can adopt those better terms. An uncapped SAFE has no valuation cap at all—the investor just gets whatever discount applies (typically 20 percent) at the Series A. The MFN provision means if you later issue SAFEs to other investors with a cap, this investor can choose to either take the discount or the cap, whichever is better.

Y Combinator's current standard is something like $125,000 on a post-money SAFE with a capped valuation of around $1.8 million (which works out to roughly 7 percent equity for a typical Series Seed company), and then $375,000 on an uncapped MFN SAFE. This creates a situation where Y Combinator has a capped position and an uncapped position with MFN rights.

The danger here is that most-favored-nation clauses create hidden dilution. If you issue a SAFE to another investor with a $6 million cap and a 20 percent discount, your Y Combinator MFN SAFE holders might choose to adopt that $6 million cap too. Now you've effectively given Y Combinator access to better terms without renegotiating. Over multiple rounds, MFN clauses can compound.

My advice: understand what MFN means before you sign it. And when you're negotiating SAFEs with other investors, be aware that broad MFN clauses can ratchet down your terms across your entire cap table.

The Administrative Nightmare: Side Letters, Pro Rata Rights, and Cap Table Complexity

SAFEs were supposed to be "simple," and technically, the SAFE agreement itself is usually just a few pages. But in practice, the simplicity often evaporates immediately. This is because investors want additional protections and rights beyond what the SAFE itself provides, so you end up with side letters.

Side letters typically cover things like pro rata rights (the right to invest in your Series A to maintain their current ownership percentage), information rights (the right to get financial updates), board observer rights, and other protective provisions. These start out seeming reasonable, but they accumulate.

I've seen founders who raised capital from five or six different SAFE investors end up with five or six different side letters, each with slightly different provisions. Now your Series A is coming, and you're managing a complex web of pro rata obligations, information rights requests, and board observer appointments. Your Series A investor wants to clean this up, so you're negotiating to eliminate or consolidate side letters at the same time you're closing the Series A. It's a mess.

My advice: be thoughtful about side letters. Yes, most investors will ask for them. But you can—and should—push back on ones that don't make sense. Pro rata rights are standard and reasonable, but consider limiting them to the next round only, not perpetually. Information rights are fine. Board observer rights are usually fine too, though it adds administrative overhead. But things like anti-dilution provisions, voting rights, or liquidation preferences in side letters? Those can create real problems. Negotiate them down or push back entirely.

The Dilution Problem: Why You Need to Model Your Cap Table Before Signing

This is the mistake I see most often, and it's the most expensive one. Founders raise a SAFE, then another SAFE, then maybe a third one, without actually calculating what their cap table will look like when all of these SAFEs convert at the Series A.

Let me give you a realistic example. You raise $250,000 on a post-money SAFE with a $5 million cap. Your SAFE holder owns $250K / $5M = 5 percent. Later, you raise another $250,000 on a post-money SAFE with an $8 million cap. That investor owns $250K / $8M = 3.125 percent.

Now you raise a Series A at $30 million pre-money and $35 million post-money (raising $5 million). Your first SAFE holder converts at their $5 million cap, getting shares equal to $250,000 / (the Series A per-share price determined by the $5M cap). Your second SAFE holder converts at their $8 million cap. After conversion and dilution from the Series A, your Series A cap table looks something like: your SAFE holders own 5% and 3.125%, Series A investors own some percentage, and you and your co-founders own the rest—which might be substantially less than you thought.

I've seen founders give away 40 percent of their company to pre-Series A investors (through stacked SAFEs and early angel investments) because they didn't model the dilution. When the Series A comes and they see their ownership percentage, they're shocked. And at that point, it's too late to undo the SAFEs.

Don't let this be you. Before you sign a SAFE, model your cap table. Assume you're going to raise more SAFEs. Assume your Series A will happen at a valuation higher than your SAFE caps. Calculate what your ownership percentage will be. If it's not acceptable, negotiate the caps before you sign.

SAFE vs. Convertible Note: Which Should You Use?

If you're considering a SAFE, you might also have the option of taking a convertible note instead. What's the difference, and which is better?

A convertible note is debt. It has a maturity date (usually 24 to 36 months), an interest rate (usually 2 to 8 percent), and conversion terms. If the company raises a Series A before the maturity date, the note converts into Series A shares at the conversion terms. If the company doesn't raise a Series A by the maturity date, the investor can demand repayment—or in practice, you renegotiate.

A SAFE, as I explained earlier, has no maturity date, no interest, and no debt characteristics. It just converts when certain conditions are met.

For founders, SAFEs are generally preferable. You don't want to carry debt on your balance sheet, especially as a startup. You don't want the psychological pressure of a maturity date hanging over your head. And you don't want to worry about an investor demanding repayment if you don't hit your Series A timeline.

However, some investors prefer convertible notes because of that maturity backstop. If they're putting money in and the company doesn't raise a Series A, they want some mechanism to get their money back or force a liquidity event. A SAFE offers no such protection.

In practice, SAFEs have largely won the market. Most early investors now prefer them because they're simpler and faster to close. But in some situations, especially if you're dealing with more traditional angel investors or institutional investors, you might encounter convertible notes.

One nuance worth noting: there are some jurisdictions where SAFEs have securities law implications that convertible notes don't, simply because of how the instruments are legally structured. This is one area where I'd strongly recommend getting legal counsel before you finalize your financing strategy.

The Common Mistakes Founders Make—And How to Avoid Them

After decades of working with founders on financing, I can tell you the mistakes tend to cluster around a few themes.

First, stacking too many SAFEs without modeling. I've mentioned this, but it bears repeating. Run the numbers. Model multiple scenarios. See what your cap table looks like in a successful outcome and a mediocre outcome. If you don't like what you see, renegotiate before you sign.

Second, agreeing to side letters that give away too much. Not every investor needs a side letter. And not every side letter provision should be granted. Push back. You're the founder. You have more leverage than you think, especially if you're raising from multiple sources.

Third, not understanding post-money SAFEs. Many founders still think of SAFEs as pre-money instruments or don't fully grasp that the SAFE holder's ownership percentage at conversion is fixed. This leads to surprise and frustration at the Series A. Understand the math.

Fourth, setting the valuation cap too low out of desperation. Yes, you need capital. But giving it away on terms that don't reflect even a reasonable guess at your company's trajectory is a bad deal. Take a breath. Negotiate. Walk away if you need to. There will be more fundraising opportunities.

Fifth, not thinking about 409A valuations. If you're granting stock options to employees after you've raised SAFEs, the valuation cap might set a floor for your 409A valuation (the IRS's assessment of your fair market value). This can create problems if your cap is much lower than what the IRS thinks you're worth. Talk to a tax attorney about this.

When You Absolutely Need a Lawyer

SAFEs were designed to be simple so founders could close them quickly without legal help. And for the SAFE document itself, they're generally pretty straightforward. But the strategic questions around SAFEs—what cap is reasonable, how many should you raise, what side letters should you agree to, how will this all look at your Series A—these require lawyer-level thinking.

I'm obviously biased, but I'd strongly recommend getting a lawyer involved in your SAFE rounds. Not necessarily to negotiate every detail (though that's good too), but at minimum to model your cap table, review any side letters, and make sure you're not creating problems for your Series A. The difference between a founder who really understands their cap table dynamics and one who doesn't is the difference between someone who makes smart decisions at the Series A and someone who's shocked and scrambling.

A good startup lawyer will also help you think about the tax and securities implications of your specific structure, which varies depending on your jurisdiction, entity type, and other factors.

The Bottom Line

SAFEs have become the dominant instrument in pre-seed and seed financing for good reason: they're fast, they're relatively simple, and they align incentives between early investors and founders. But "simple" doesn't mean "uncomplicated," and it definitely doesn't mean you can sign one without thinking.

Understand what you're signing. Know the difference between post-money and pre-money. Model your cap table with multiple SAFEs. Negotiate the valuation cap thoughtfully. Be selective about side letters. And if there's any doubt, get a lawyer to review the full package.

Your pre-Series A capital decisions shape your entire company's future. Make them deliberately.

If you're raising capital or navigating SAFE agreements, I'd recommend getting a lawyer who understands both the legal and practical sides of early-stage financing. I offer free introductory calls to discuss your specific situation and help you think through your options.

Book a free introductory call with me to discuss your startup's financing strategy.

For more on startup fundraising and securities law, see our Complete Guide to Regulation D, Rule 506(b) vs. 506(c) Comparison, and Accredited Investor Rules.

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