Find the right co-founder, the evidence-based way
Cofounnder turns “do I trust my gut?” into a structured, guided evaluation, so you commit to a partnership with evidence, not just a good feeling.
Two modes, whether you have the idea or you’re the builder.
The problem
Most co-founder break-ups were predictable
The idea rarely kills a startup. The partnership does. Yet founders evaluate a potential co-founder with far less rigour than they'd apply to a single engineering hire.
65%
of high-potential startups are estimated to fail because of co-founder conflict, not the product.
Months
of equity, time, and momentum are on the line before most founders ever stress-test the relationship.
Gut feel
is still how most pairs decide, a few coffees, shared excitement, and a handshake.
The exact numbers vary by study, but every founder who’s lived through it tells the same story.
Two ways in
Whichever side of the table you're on
Cofounnder meets you where you are. Pick the mode that matches your role, and the evaluation adapts to the questions that matter for your side of the partnership.
You have the idea
Idea Mode
You've got the vision and you're looking for the builder who can bring it to life with you. Define what the venture needs, then evaluate whether a candidate truly fits, on capability, commitment, and chemistry.
- Articulate the idea, stage, and the gaps you need a partner to fill
- Assess builders against what the venture actually demands
- Surface red flags before equity changes hands
You're the builder
Builder Mode
You can build, now you're choosing whose vision to bet your time on. Pressure-test the idea, the person behind it, and whether the partnership terms are worth your runway.
- Evaluate the idea and the founder, not just the pitch
- Clarify your own non-negotiables before you commit
- Decide with evidence whether to build together
How it works
Four phases. One clear decision.
Cofounnder guides both of you through a structured evaluation, gathering evidence across the four areas that make or break a founding partnership, then turning it into a decision you can stand behind.
- PHASE 01
Alignment
Vision, values, motivation, and commitment. Are you actually building toward the same thing, for the same reasons, at the same intensity?
- PHASE 02
Capability
Complementary skills, track record, and the gaps each of you fills. Does the pairing cover what this specific venture demands?
- PHASE 03
Working dynamics
Communication, conflict, decision-making, and trust under pressure. How will you actually operate when things get hard, because they will?
- PHASE 04
Terms & commitment
Roles, equity, expectations, and runway. The practical, often-avoided conversations that decide whether goodwill survives reality.
The decision
A clear Go / No-Go
No more agonising in circles. The evaluation resolves into an honest recommendation, proceed, pause, or walk away, grounded in what you actually uncovered, not how excited you felt that week.
The artefact
A Partnership Report
A shareable summary of where you align, where you differ, and the conversations still worth having, so even a “no” leaves you wiser, and a “yes” starts on solid ground.
What you get
Rigour, without the consultant price tag
Everything in Cofounnder exists to do one thing: help you make the co-founder decision with the seriousness it deserves.
Evidence over instinct
Every phase asks for specifics, not vibes. You finish with reasons you can point to, not a feeling you can't explain.
Guided prompts
Thoughtful, sometimes uncomfortable questions you'd never think to ask on your own, surfaced at the right moment.
Built for both sides
Idea Mode and Builder Mode adapt the evaluation to your role, so the questions always fit your stake in the partnership.
A report you can share
Turn the whole evaluation into a clean Partnership Report, useful for the hard conversations, and for your own clarity.
Honest red-flag surfacing
Cofounnder is designed to help you see what excitement hides, the misalignments that only show up months in.
Private by default
Your evaluations are yours. We collect only what the experience needs, and you can delete your account and data at any time.
FAQ
Questions, answered
Is Cofounnder a matching app like dating for co-founders?
Not quite. Cofounnder is an evaluation tool. Once you have someone in mind, or you're considering an introduction, it helps you decide whether the partnership is right, with a structured process instead of gut feel.
Do both people need to use it?
You can get real value running the evaluation yourself. But the process is most powerful when both potential co-founders engage with it together, that's when the honest, partnership-defining conversations happen.
What's the difference between Idea Mode and Builder Mode?
Idea Mode is for when you have the venture and you're evaluating a potential builder. Builder Mode is for when you bring the execution and you're deciding whose idea, and whose partnership, to commit your time to. The questions adapt to your role.
Does it use AI?
Yes. Cofounnder uses AI to help guide the evaluation and shape your Partnership Report. We disclose our AI provider in our Privacy Policy. Your inputs are used to deliver the experience, not sold.
How much does it cost?
Pricing will be announced ahead of launch. Any paid plans will be handled through the App Store and Google Play.
Who is it for?
Cofounnder is for adults (18+) seriously considering a startup partnership, first-time founders and repeat founders alike.
Don’t bet years on a hunch
The right co-founder can make a startup. The wrong one can end it. Give the most important decision the rigour it deserves.
Free on iPhone. Android coming soon.