Blok just launched out of stealth with an AI tool that simulates user personas to test app features before launch. Developers upload event data from platforms like Amplitude, Mixpanel, or Segment. Then Blok creates AI-driven personas to run simulations on new features and deliver reports on what works and what doesn’t.
Founders Tom Charman and Olivia Higgs built Blok to replace slow, reactive A/B testing with predictive user behavior modeling. The startup has raised $7.5 million so far, including a $5 million seed led by MaC Venture Capital with backing from folks at Discord, Google, Meta, Apple, Snapchat, and Pinterest.
Marlon Nichols at MaC Venture Capital called Blok a step ahead of tools like Optimizely and Amplitude by offering a predictive layer for product testing. 
“We backed Blok because we believe product development is at an inflection point. Teams are shipping faster than ever, but they’re still making critical decisions based on A/B tests and gut instinct. Blok’s simulation engine flips that model — giving teams the ability to predict user behavior before a single line of code is written.”
Higgs highlighted the rising need for better testing as apps get more complex, mixing chat, voice, and visual interfaces.
“There is a real need for increased testing because the bar for visual interfaces is getting a lot higher. We’re seeing people interact with technology through chat, through voice. So if you’re introducing visual UI [elements] into the mix, you have to make sure that you are not introducing unnecessary friction into a user’s workflow.”
Blok is targeting companies big and small. Smaller outfits lack live user testing cohorts. Larger companies want to avoid bloated apps stuffed with features.
“We are trying to reach a place where companies don’t need to release their features on an experimental basis and wait for a few weeks or months for results to show up,” said Charman.
The tool uses uploaded Figma design files along with experiment details—like hypotheses and user goals. AI personas then simulate use and churn out insight reports, with persona-specific feedback and chatbot access for queries.
Blok is currently behind a waitlist, working mostly with finance and healthcare startups to avoid risks from public beta testing.
The company charges via SaaS, aiming for mid-single-digit million revenue this year. It’s still balancing high compute costs from the simulations but plans to expand its customer base soon.
