The first tool I’ve created is the CRO-tool. All psychology theories in one place. With the first feature of this tool is that you can search for theories. You can use these theories to optimize any website. The theories are explained very well and containing examples of how you could apply this theory. Let me explain how this tool solves a certain problem, how it came into existence and what the future might hold for it.

Table of contents:

Let’s start with the first chapter!


During the start of 2018 I got interested in conversion rate optimization also known as CRO. CRO is basically optimizing websites to they increase certain goals you have with your website, the goal that’s mostly used is increase sales (for e-commerce companies) but you could also think of goals like increase number of email subscriptions or increase account registrations on your website.

CRO is data driven and you can’t get away with ‘I feel we should do this’. With CRO you’ll always write a hypothesis which is based on data before testing if something works. Testing is part of the CRO process, you’ll always tests if the assumptions you’ve made are true.

Around June 2019 I did a Conversion Specialist course at Online Dialogue, one of the best known CRO companies within the Netherlands, if not Europe, if not the World probably. They write hypothesis in a way that includes UX, data (metric), type of audience, device and psychology. Learning how and why they do it made me sure that I would never write my hypothesis any other way anymore.


The hard part about writing a hypothesis for CRO is the psychology part. It isn’t easy to start integrate psychology into your hypothesis without having a degree or years of experience in it. There is so much knowledge out there on the internet that’s hard to figure out which information is trust worthy without having to check all the sources.

There was a list I had which contained all the short summaries for about 200 psychology theories. But I still didn’t know when to use what theory and the overview was to long to go by every time I wrote an hypothesis. I think you’re starting to feel it, that’s the point where I came up with creating a search engine specifically for psychology theories.


One day I sat down and wrote down the idea I had. Afterwards I pitched it too, now the co-founder, Roelof Jan. He was enthusiastic about it. We’re not people that want to build products, so it took us some time but we’ve launched an Alpha version around April 2020.

The solution became the search engine including over 300 psychology theories that can be used for CRO. The theories are split in tree categories called decision making, memory biases and social biases. Every theory contains content about the theory, examples of hypotheses, references but also theories that overlap that might be interesting.

The best thing, it’s all available for for free!


The search engine is part of a bigger tool we are creating for CRO/UX and maybe everybody who would like to write hypotheses.

We’re aiming to become the number one documentation tool for CRO and UX specialist. This includes documenting your research, hypothesis and integrating the data of all the tests you might be doing. We’re even thinking of integrating some extra tools to collect data, but that’s nowhere near the surface yet.


Are you curious about my responsibilities with this project? I’m the one that’s responsible for the UX/UI design, research, front-end development partly, wire-framing, content, new features, marketing and so on.

I couldn’t have done this without the co-founder Roelof Jan. He’s responsible for some of the front-end development, all of the back-end development, server related stuff, technical SEO etc.

It’s very nice that we can combine all our skills and are able to create full products without needing external people.


This tool is created by Roelof Jan and I, but we couldn’t have done it without the feedback of people from out network and multiple communities. There are so many people that would like to help us with the tool that we are motivated to make this tool to a success, to make documentation easier for everybody.