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The Simple Agreement for Future Equity (SAFE) is a financing instrument created by Y Combinator in 2013 that revolutionized early-stage startup investing. It’s simpler than convertible notes, with no interest rate, maturity date, or repayment obligation.
SAFEs are not debt. They’re not equity either. They’re a contractual right to receive equity in the future, typically when you raise a priced equity round or have a liquidity event.

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Why SAFEs exist

Y Combinator created SAFEs to address problems with convertible notes:
Convertible notes are unnecessarily complex for early-stage rounds:
  • Interest rates that must be calculated
  • Maturity dates that create artificial pressure
  • Debt classification with repayment obligations
  • Negotiation over multiple financial terms
SAFEs eliminate this complexity:
  • No interest calculation
  • No maturity date
  • No repayment obligation
  • Fewer terms to negotiate
The entire SAFE agreement is typically 5 pages compared to 20+ for a note.
SAFEs were designed to be fair to founders:
  • No debt on your balance sheet
  • No pressure from approaching maturity dates
  • No requirement to pay interest if you’re profitable
  • Simple conversion mechanics
This aligns investors with long-term company success rather than short-term debt repayment.
With fewer terms to negotiate and simpler documents:
  • Term sheet discussion takes hours, not days
  • Legal review is faster and cheaper
  • No complex financial modeling needed
  • Closing can happen in days
This matters when you’re trying to get back to building your product.
Since Y Combinator launched SAFEs:
  • Thousands of startups have raised capital via SAFEs
  • Most top accelerators use SAFEs as their standard
  • Angel investors widely accept them
  • Many VCs use SAFEs for pre-seed/seed bridge rounds
SAFEs have become the market standard for very early-stage investing.

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SAFE variants

Y Combinator offers four standard SAFE templates, each with different economic terms.
Most common SAFE structureThe SAFE converts based on a valuation cap:
  • Sets maximum conversion valuation
  • No discount on equity round price
  • Simple and clean
Example:
  • SAFE: 100Kinvestmentat100K investment at 6M cap
  • Series Seed: Raises 2Mat2M at 8M pre-money, $1.00/share
  • SAFE converts at: 6Mcap÷8Mshares=6M cap ÷ 8M shares = 0.75/share
  • SAFE gets: 100K÷100K ÷ 0.75 = 133,333 shares
When to use:
  • Standard for most pre-seed and seed rounds
  • Clean cap table math
  • Easy to explain to all parties
This is the most popular SAFE variant. If you’re unsure which to use, start here.

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Post-money vs. pre-money SAFEs

In 2018, Y Combinator updated their SAFE to use “post-money” valuation mechanics, which are clearer and more founder-friendly.
How they worked:
  • Cap was treated as pre-money valuation
  • SAFE holders diluted each other
  • Cap table math was confusing
  • Could result in unexpected dilution
Example of the problem:
3 SAFEs invest $100K each at $6M cap
Series Seed raises $2M at $10M pre-money

Question: What % does each SAFE get?
Answer: Complicated, and SAFEs dilute each other
Y Combinator deprecated pre-money SAFEs in 2018. Don’t use them.
How they work:
  • Cap represents post-money valuation
  • SAFE investors don’t dilute each other
  • Crystal clear ownership calculation
  • Predictable cap table impact
Simple math:
SAFE invests $1M at $10M post-money cap

Ownership = Investment ÷ Cap
          = $1M ÷ $10M
          = 10% of company (precisely)
This is the SAFE you should use. It’s simpler and more predictable for everyone.
Always use post-money SAFEs. They’re the current standard and eliminate confusion about dilution.

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How SAFEs convert

SAFEs convert to equity when specific events occur. Understanding these mechanics is crucial.

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Equity financing conversion

1

Equity financing triggers conversion

When you raise a “Equity Financing” (typically any preferred stock round), all SAFEs automatically convert.Qualified as Equity Financing:
  • Sale of preferred stock
  • Principal purpose of raising capital
  • Typically $1M+ minimum threshold (negotiable)
Not Equity Financing:
  • SAFE conversions themselves
  • Stock option exercises
  • Convertible note conversions
  • Strategic partner stock issuance (usually)
2

Calculate conversion price

Post-money SAFE math:Conversion Price = Post-Money Valuation Cap ÷ Company CapitalizationWhere Company Capitalization includes:
  • All outstanding stock (common and preferred)
  • All outstanding options and promises (converted to common)
  • All convertible securities (SAFEs, notes) as-converted
  • All shares reserved under option pool
Example:
  • SAFE: 500Kat500K at 8M post-money cap
  • At conversion, company has 8M shares outstanding (fully-diluted)
  • Conversion price: 8M÷8Mshares=8M ÷ 8M shares = 1.00/share
  • SAFE converts to: 500K÷500K ÷ 1.00 = 500,000 shares
3

Determine which shares SAFE receives

Standard SAFE: Converts to same stock as equity round investors
  • If Series Seed Preferred is issued, SAFE gets Series Seed Preferred
  • Same rights, preferences, and privileges
  • Same liquidation preference per share
Shadow series possible:
  • If SAFE converts at lower price than equity round price
  • Company may issue shadow series (e.g., “Series Seed-1”)
  • Identical rights to Series Seed
  • Different liquidation preference per share (1x the SAFE price)
4

Update cap table

After SAFE conversion:
  • SAFE holders become stockholders
  • Receive all rights of that stock class
  • Subject to all obligations (drag-along, etc.)
  • SAFEs disappear from cap table
Model your cap table with SAFEs converting before you price your equity round. You need to understand total dilution.

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Liquidity event conversion

If you’re acquired or IPO before raising an equity round, SAFE holders receive:Option 1 - Cash payment (most common):
  • SAFE converts immediately before transaction
  • Converts at valuation cap (or discount if applicable)
  • SAFE holder receives cash equal to their pro rata share
Example:
  • SAFE: 100Kat100K at 10M cap
  • Acquisition: Company sells for $50M
  • SAFE converts: 100K÷100K ÷ 10M = 1% of company
  • SAFE receives: 1% × 50M=50M = 500K
Option 2 - Stock in acquirer:
  • Less common
  • SAFE converts to company stock first
  • That stock then converts to acquirer stock per deal terms

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SAFE terms and negotiation

While SAFEs are simpler than notes, you still need to negotiate key terms.

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Key negotiable terms

Valuation cap

What it is: Maximum effective valuation for SAFE conversionTypical ranges by stage:
  • Pre-seed: 4M−4M - 8M
  • Seed: 8M−8M - 15M
  • Bridge to Series A: 15M−15M - 25M
Negotiation dynamics:
  • Higher cap = less dilution for founders
  • Lower cap = better deal for investors
  • Should reflect realistic Series A valuation
Your SAFE cap should be 50-70% of your expected Series A valuation. If you expect to raise Series A at 20Mpre−money,a20M pre-money, a 10-14M SAFE cap is reasonable.

Discount rate

What it is: Percentage discount to equity round priceStandard rates:
  • 15-20% most common
  • 10-15% for later-stage SAFEs
  • 20-25% for very early, high-risk
When to use:
  • With a cap: Provides floor and ceiling
  • Without a cap: Only protection for investor
If you have both a cap and discount, investors get the better deal between the two at conversion.

Pro rata side letter

What it is: Right to invest pro rata in equity financingStandard terms:
  • Available to investors of $50K-100K+
  • Right to maintain ownership percentage
  • Granted via separate side letter
  • Optional and negotiable
Founder consideration:
  • Reduces available allocation in Series A
  • May crowd out new investors
  • Can be helpful with strategic investors
See Y Combinator’s Pro Rata Side Letter template.

MFN provision

What it is: Right to better terms if offered to future SAFE investorsHow it works:
  • You issue SAFE A at $10M cap
  • Later issue SAFE B at $8M cap
  • SAFE A automatically gets $8M cap
Founder impact:
  • Limits flexibility in future SAFE terms
  • Can’t offer different terms to different investors
  • Creates parity but reduces negotiating room
MFN provisions complicate your fundraising. Try to avoid them or limit them to a short time window (e.g., 90 days).

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Information and governance rights

Standard Y Combinator SAFEs include minimal investor rights:
Standard SAFE: No information rights until conversionSometimes negotiated:
  • Annual financial statements
  • Quarterly updates
  • Major event notifications
Founder perspective:
  • Adds administrative burden
  • Not standard for SAFEs
  • Can add via side letter if needed
Most SAFE investors don’t ask for information rights. They’ll get them after conversion.
Standard SAFE: No board seat or observer rightsSAFEs don’t convey governance rights. Investors become stockholders only after conversion.Exception: Very large SAFE investors ($1M+) sometimes negotiate:
  • Board observer rights
  • Granted via separate side letter
  • Continue after conversion
Generally resist board seats or observer rights for SAFE investors. Wait until Series A.
Standard SAFE: SAFE holders don’t vote on company decisionsThey’re not stockholders until conversion. Company has full control.Very rare exception: Some large SAFEs include:
  • Consent rights for major decisions
  • Blocking rights for new SAFEs
  • Approval rights for liquidity events
Giving SAFE holders voting rights defeats the purpose of SAFEs. Avoid this.

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SAFEs vs. convertible notes

Choosing between SAFEs and convertible notes depends on your situation.
✅ Use a SAFE if:
  • Very early stage (pre-seed, accelerator)
    • You need simplicity over complexity
    • Valuation is highly uncertain
    • You want to close quickly
  • Founder-friendly market
    • Investors accept SAFEs as standard
    • You have leverage in negotiations
    • You’re in a tech hub (SF, NYC, etc.)
  • Speed is critical
    • You need to close in days, not weeks
    • Legal fees must be minimal
    • Term sheet negotiations should be brief
  • Small amounts
    • Individual checks under $250K
    • Many small investors
    • Rolling closes over time
SAFEs are the default for Y Combinator companies and most accelerator programs. If you’re pre-seed or seed, start with SAFEs.

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Common SAFE pitfalls

Avoid these mistakes when using SAFEs:
The problem:
  • Founders issue multiple SAFEs
  • Don’t model conversion scenarios
  • Surprised by dilution at Series A
Example of the problem:
Founder issues:
- $500K SAFE at $5M cap
- $750K SAFE at $6M cap
- $1M SAFE at $8M cap
Total: $2.25M on SAFEs

Series A: $3M at $12M pre-money

Founder assumption: ~20% dilution from Series A
Reality: ~35% dilution from SAFEs + Series A
The fix:
  • Model your cap table after each SAFE
  • Assume SAFEs convert at their caps
  • Plan for total dilution, not just equity round dilution
  • Use tools like Carta or Pulley
The problem:
  • SAFEs seem like “free money” (no immediate dilution)
  • Founders raise $2M+ on SAFEs before pricing
  • Creates complex cap table at Series A
Why it’s bad:
  • Series A investors see messy cap table
  • SAFEs at multiple caps are confusing
  • May require re-negotiating SAFE terms
  • Can kill your Series A
General rules:
  • Don’t raise more than $1.5M on SAFEs
  • Consider pricing an equity round sooner
  • Keep number of SAFEs manageable (fewer than 20 investors)
If you need to raise more than $2M, strongly consider pricing an equity round instead of continuing to issue SAFEs.
The problem:
  • Issuing SAFEs with different caps over time
  • Some with discounts, some without
  • Some with MFN, some without
  • Creates cap table mess
Example:
- January: $250K SAFE at $6M cap, 20% discount, MFN
- March: $500K SAFE at $8M cap, no discount, MFN
- May: $300K SAFE at $10M cap, 15% discount, no MFN

MFN triggers make this a nightmare to unwind.
Best practice:
  • Set SAFE terms at the beginning
  • Use same terms for all investors in that round
  • Only change terms for next distinct round
  • Document any exceptions clearly

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SAFE best practices

1

Use post-money SAFEs exclusively

Always use Y Combinator’s current post-money SAFE templates. Never use pre-money SAFEs.Download from Y Combinator.
2

Start with cap-only SAFEs

Unless investors specifically request a discount, use the “Valuation Cap, no Discount” SAFE.It’s cleaner, simpler, and easier to explain to future investors.
3

Set a realistic valuation cap

Your cap should be 50-70% of your expected Series A valuation. If you think Series A will be $20M pre-money:
  • SAFE cap range: 10M−10M - 14M
  • Too low: You over-dilute
  • Too high: Investors won’t participate
4

Keep excellent records

For each SAFE, maintain:
  • Signed SAFE agreement
  • Wire transfer confirmation
  • Board consent approving the SAFE
  • Form D filing (if required)
  • Updated cap table
Use a service like Carta, Pulley, or Clerky to manage SAFEs.
5

Communicate with SAFE holders

Even though SAFEs don’t require information rights, keep investors updated:
  • Quarterly email updates
  • Major milestone announcements
  • Heads up before equity financing
These investors believed in you early - keep them engaged.
6

Plan your equity round

Before raising your equity round:
  • Model full dilution including all SAFEs
  • Understand how SAFEs will convert
  • Set Series A price that works with SAFE conversion
  • Consider whether you need to adjust option pool
Surprises at equity financing are bad for everyone.

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Resources and templates

Y Combinator SAFE templates

Download all four SAFE variants and the Pro Rata Side Letter template

SAFE User Guide

Y Combinator’s comprehensive guide to post-money SAFEs with examples

Clerky SAFE service

Automated SAFE preparation and filing service for startups

Cap table tools

Model SAFE conversion with:

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Next steps

Convertible notes

Compare SAFEs to convertible notes and understand when to use each

Equity term sheets

Learn about equity financing and how SAFEs convert in priced rounds

Cap table planning

Understand dilution and plan your cap table through multiple rounds

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