Karol Brennan Headshot

Hi! My name is Karol Brennan

I'm a software developer from Milwaukee, Wisconsin

I created the #1 global bingo calling application letsplaybingo.io.

I'm currently building highly customized sites in Salesforce Experience Cloud at Slalom.

Recent things I've worked on.

After spending the last several years working within consulting the vast majority of what I have built is proprietary. If you have any questions about the types of projects I've been involved in please ask!

Throughout my career I have have the opportunity to work on projects of all sizes for companies ranging from big tech and fortune 500s, to small businesses and non profits. I enjoy the unique challenges that each project brings.

I do maintain some open source work on my GitHub if you'd like to check out some of my code.

Let's Play Bingo




Originally created in 2017 as a vanilla Javascript application, I rebuilt it in ReactJS in 2018. Let's Play Bingo has since grown to have over a million lifetime users and is now the #1 bingo caller on Google! It is used by people in over 150 countries all over the world to facilitate games at home with friends or in bingo halls.

ReactJS Sass Javascript HTML5 CSS3

Hulu Community


Salesforce Experience Cloud

Senior Front-End Developer

I built many custom features across 3 years of partnering with Hulu. The most recent of what I worked on can be viewed at Hulu's Community. I worked with another developer and built a completely custom Salesforce chatter feed which you can see in action in the Questions and Community News portions of the site.

Apex Lightning Web Components Aura HTML5 CSS3 Javascript

My Current Roles

A Girl Created This, LLC

Owner / Developer

May 2020 - Current

Developed the #1 “free bingo caller” application on Google called Let's Play Bingo.

  • Originally written in January 2017 using pure object oriented JavaScript.
  • Refactored to a single page ReactJS app in 2018 leveraging Sass and a custom grid system.
  • LPB currently receives an average of 40k users per month across 150+ countries.


Senior Consultant / Developer

May 2022 - Current

Served as a subject matter expert on the Salesforce Experience Cloud team.

  • Developed highly customized Salesforce Experience Cloud sites for a variety of clients.
  • Established an internal component respository used to accellerate project development.
  • Established coding standards for the team and drove conversations surrounding best practices.
If you're interested in my full professional history, check out my LinkedIn profile.

You can also download a copy of my full resume.

A little more about me.

Throughout my career I've worked as a Salesforce developer, front-end / ReactJS developer, full stack PHP developer, and web designer. I found my passion in bringing designs to pixel perfect fruition on the front-end through HTML, CSS and JavaScript.

I am a minimalistic developer, prefering to use vanilla JavaScript and plain CSS when possible. I only reach for a framework when there is something to gain from them. Usually for more complex component driven projects. My current framework of choice is ReactJS, which I have been using for my side project letsplaybingo.io since 2018. I often employ Sass for CSS pre-processing and like to use my own simple grid system in my personal work instead of something like Foundation or Bootstrap. I enjoy component driven development, object oriented programming concepts, and new challenges that require abstraction and data manipulation.

Outside of my career - I am happily married and I am the proud mama of 2 awesome kids and 2 goofy doggos. I believe in equality, kindness, and helping others. I care about sustainability, animal rights, and human welfare. In my spare time I enjoy gaming and gardening. I run on plants, water, and sarcasm.

Let's connect!

Connect with me on LinkedIn.
Follow my open source work on GitHub.
Check out my full resume.
Wanna chat about something else? Send an email to hello at karol.dev.