Character Labs

Character Labs is the only startup accelerator that’s 100% focused on product-market fit

Since 2011, we have helped the world’s most successful startups build and launch products with our Design Sprint and Foundation Sprint methods.

We combined lessons and techniques from our work with 300+ companies into Character Labs. If you want to build a differentiated AI product that really works for customers, you should apply for Character Labs today.

Now accepting applications for Character Labs G5, starting November 3.

Apply Now

In Character Labs, you’ll work directly with our team: Jake Knapp and John Zeratsky, creators of the Design Sprint and Foundation Sprint, bestselling authors of Sprint and Click, and former design partners at Google Ventures; and Eli Blee-Goldman, our co-founder and general partner leading all investments at Character.

As investors and designers, we have worked closely with more than 300 startups, including Flatiron Health, Gusto, YouTube, Phaidra, Fathom, Miro, and Slack, through pivotal moments in their growth.

We’ll be there the whole time, personally leading you through six weeks of hands-on sprints.

We’ll also be joined by customer research expert Jeanette Mellinger, Character portfolio founders, and AI experts from DeepMind, Google, and more.

Through a sequence of back-to-back sprints, you’ll find out whether you’re on the right track in just a few weeks:

First, a Research Sprint — use structured interviews and “free prototypes” (i.e. the competition) to build your customer intuition.
Next, we’ll run a Foundation Sprint — identify and capture the opinionated hypotheses behind your product or company.
Then, a sequence of Design Sprints — each week, you’ll build a prototype and test it with real customers.
Update your Founding Hypothesis as you validate the key risks with each sprint.
Repeat and iterate until it ”clicks” consistently with customers.

Character Labs combines everything we’ve learned from working with 300+ startups. It expands on the proven method from our books Sprint and Click with new techniques that we haven’t shared publicly.

For a behind-the-scenes look at Character Labs, check out our interview on Lenny’s podcast:

Every startup in Character Labs gets a $150,000 investment from Character in exchange for 5% equity. We make our investment on the day of acceptance. It‘s not contingent on any milestones, and there are no fees to participate.

We’ve carefully designed this offer. Because of the hands-on work we do alongside you and your team, we believe it’s a better value than other accelerators, and it’s small enough to sit alongside capital from other sources with minimal dilution.

We accept a maximum of 15 companies into each Character Labs group. You'll work directly with the founding partners of our firm. This is an elite, hands-on, high-quality experience for exceptional founders — not a startup factory.

Like any good investor, we'll help you with customer introductions, hiring, and fundraising when the time is right. We know how valuable that support can be when you're building something new.

But we also know none of it matters if you don’t get the product and go-to-market right.

That’s why Character Labs is 100% focused on helping you find product-market fit, and why it’s all about doing — not talking.

FAQs

Who should apply?

Character Labs is designed for startup founders who have identified an opportunity or market, but have not found product-market fit.

That could mean you have an early product in the market but it’s not quite working, or that you haven’t shipped your v1 yet.

Either way, you know how important it is to build the right product for the right people, and you love the idea of a focused effort to figure it out.

If you’re not sure whether Character Labs is a good fit — apply! (Please note that we only invest in software products and software-enabled services.)

Why is Character Labs a good fit for AI startups?

In the age of AI, anyone can build anything — fast. But founders today face two important challenges: Cutting through the noise and reaching customers in a competitive landscape that’s more crowded than ever, and creating products that actually deliver on the promised value for customers.

We’ve seen these challenges firsthand, as investors and designers in healthcare, personal finance, manufacturing, and consumer apps, and more.

We have led Design Sprints for successful AI products since 2009, when Jake designed Gmail’s Priority Inbox. We worked with AI teams from Flatiron Health, Digit, Orbital Materials, Phaidra, and more. Our portfolio includes startups founded by AI engineers from Google DeepMind, Microsoft, and Amazon.

To meet customer expectations that are growing by the minute, successful founders obsess over quality. And to capture customer attention in ever-more-crowded markets, they dig deep for differentiation — reframing the value proposition in ways that really click for customers.

Again and again, we’ve seen how effective Foundation Sprints and Design Sprints can be meeting both of these challenges. And we think it’s the perfect time for a program that helps AI founders bring their work closer to the humans they are building it for.

Plus, we’re nerds at heart, and just love being part of what’s next in technology 🤓

Do I need a team to apply?

Technically no, but ideally yes.

Character Labs is not an incubator. Our goal is to support and empower you and your team to accelerate progress toward product-market fit — not replace or stand in for your team.

We may accept solo founders but have a strong preference for teams.

Character Labs is also a great opportunity to build your team. You can use the four weeks to test out working with potential co-founders or teammates.

We recommend teams of 2–3, including people who can rapidly build scrappy prototypes and are comfortable talking to customers.

I’m outside the USA. Should I apply?

Maybe! Character Labs includes three days in San Francisco, but the rest of the program is fully remote.

However, please keep in mind that all synchronous sessions will take place on USA time, roughly 10am to 4pm Central Daylight Time (that's UTC–5) on most days of the program. (See below for details.)

Also, at this time we are only able to invest in companies incorporated in the USA.

What is the application timeline?

Applications are due at 11:59pm Central Time on September 24, 2025.

We review applications in the order they are received and give priority to earlier applications.

If you're selected to interview for Character Labs G5, we’ll be in touch by September 29 at the very latest.

If you’re selected to join the program, the absolute latest you will find out is October 6.

Character Labs begins on Monday, November 3 and runs for approximately four weeks. (See below for more details.)

Where does Character Labs meet?

Character Labs is a hybrid program that meets online and in San Francisco.

What is the program schedule?

November 3–7 • REMOTE
Research Sprint. Structured interviews and testing “free prototypes” (i.e. the competition) with customers will help you rapidly build your founder intuition.

November 12-14 • IRL in San Francisco
Foundation Sprint. Identify and capture the opinionated hypothesis behind your product or company. Use radical differentiation to create extreme separation from the competition.

November 17–21 • REMOTE
Design Sprint. Build a realistic prototype of your product or marketing and test it with real customers. Update your Founding Hypothesis based on what you learned.

November 24–28 • REMOTE
Thanksgiving Flex Week. Iterate on your prototypes, line up new customers interviews, catch up on other work, or take some time off for the holiday.

December 1–5 • REMOTE
Design Sprint. Update your Founding Hypothesis, iterate on your prototypes, or start over, and test again with a fresh batch of target customers.

December 8–9 • REMOTE
Flex Days. Run another Design Sprint or focus on other work.

December 10 • REMOTE
Risk Roadmap. Building something new is all about navigating the unknown. Make a Risk Roadmap so you know exactly what you need to validate in order to keep moving forward.

December 11–12 • REMOTE
Pitch Sprint. Synthesize your work in Character Labs and pitch it to other founders in the program. Decide what to do next and celebrate all that you've accomplished!

If you want to see more of what happens in Character Labs, check out this interview on Lenny’s podcast, where we go step-by-step and show real examples from portfolio companies.

What happens after Character Labs?

We recommend four six weeks of weekly 1:1 office hours with our team. This provides a venue for detailed, high-frequency coaching on additional sprints or fundraising, product feedback, and advice on any important decisions you're making.

Of course, this isn't the end of our work together. You’ll be a full member of the Character portfolio and have access to our network of founders, advisors, and coinvestors. We’ll continue to support you on product, GTM, strategy, hiring, fundraising, and whatever else you need.

Does this replace other accelerators or financing?

Not necessarily.

We designed the program to complement other sources of capital or startup support. At only 5% equity, your dilution is minimal relative to the value you‘ll receive in Character Labs. We're confident we'll increase your odds of success by way more than 5%!

Previous Character Labs founders have raised a pre-seed round before joining the program. Others incorporated for Character Labs, and we were their first investors. Many have gone on to raise pre-seed or seed rounds within the months following the program or participated in other elite accelerators.

Will you invest in my next round?

Yes!

We commit to investing at least our pro rata share in your next round of financing after Character Labs. In many cases, we invest more than our pro rata — although we recognize this additional allocation must be earned, and we don't take it for granted.

Now, some fine print: Our follow-on investment is triggered by a proper round of VC financing, with a price or cap set by an outside lead investor.

What if Character Labs isn’t right for me?

We’d love to hear from you anyway! We lead and co-lead a select number of seed rounds, with a maximum check size of $2 million. Please get in touch via our website.