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About us

Sherlo is a visual regression testing tool for React Native. It shows you every visual change in your UI, so none of them reach users unreviewed. It is used in production by React Native teams, from fintech to social apps.

Why we built it​

Sherlo started as an internal tool. We were working on React Native apps and kept running into the same arithmetic: every UI change should be checked on every screen, across devices and both platforms, on a range of OS versions, and in every theme and language. Multiply that out and there is more than any team can check by hand. So nobody tries, and visual bugs slip through.

We wanted our UI running on real iOS and Android simulators, not React Native rendered in a browser and diffed with a web tool. It also had to live in the cloud. Running that matrix locally ties up your machine while it works, and leaves the results where your team cannot review them. Almost everything we found was made for the web. What we had written for ourselves turned out to be worth building properly.

Who builds it​

Sherlo is built by Devine, the company we founded in Szczecin, Poland.

Michał Ziółkowski and Dawid Krajewski
Michał and Dawid playing chess in Mallorca

We are Michał Ziółkowski and Dawid Krajewski. We both took a bachelor's in computer science, at the same university and in the same years, and we have been building things together ever since. Sherlo was not the first thing we tried to build. It is the one that came out of a problem we had ourselves.

Between us we have more than twenty-five years of engineering. Michał has worked on mobile since the beginning of his career: native Android first, then React Native at Feeld since 2019. Dawid has spent most of his career on the web, including six years at home.pl leading the front-end of a design system where changing one config file restyles the whole product across brands.

As co-founders we own Sherlo day to day, and along the way designers, UX specialists, engineers and marketers have contributed to it as well. Our thanks to all of them.

All of that work points one way. We are not building a visual testing tool that happens to support React Native. We are building the one React Native deserves.