A picture from Mozilla Festival 2014. All participants are in a circle.


I'm Errietta Kostala and I'm a full stack developer...

with a passion.

Learn more

Ever since I was a teenager, I knew I wanted to be involved in programming. I spent countless hours working on my own projects, learning more and more and becoming more and more fascinated. To me, programming is an art form, a poem, a song, a dance.

But in time, it became something even more. As I started getting involved in freenode, Mozilla, and other open source projects, it became a way to be part of a community - I could network, make friends, and meet people that would be with me for the rest of my life.

It then became clear to me - I didn't just want to follow my passion of programming. I wanted to teach others what I knew. And I wanted to keep supporting Open Source projects and helping others.

For this reason, I'm studying Web Technologies at the University of Huddersfield - so that I can learn even more about what I'm passionate for. I am doing an an internship for Shadowcat Systems - a small company in Lancaster that holds open source and community projects very dearly, and I still spend a lot of my time on community projects.

Do you want to learn more about me? Check out my projects or my blog.

Latest blog posts

[vlog] Home-made hexbugs!

The long-awaited Mozfest 2015 post!

As I hope you know, Mozfest 2015 took place from November 6 to November 8 2015 at Ravensbourne UK. Mozfest is organised by Mozilla, but it is not entirely about Mozilla products. Instead, it aims to get people together talking about policies Mozilla cares about as an organisation – such … Continue reading

Dear circuit laundry: your UX SUCKS!

Ah, the joys of student life. Not only is accommodation absurdly expensive (Over 100 pounds a week to live near campus outside London. I’m not going to mention London prices, because anybody who doesn’t already know them is going to have a heart attack.), but laundry costs on top of … Continue reading

To me, no localisation is better than bad localisation.

I am Greek, and when I lived in Greece and had my system language to Greek, the first thing I would usually do would when installing a piece of software or visiting a website that realised the fact that I’m Greek would be to ensure it’s set to English. The … Continue reading

Firefox OS App building workshop

Hello world   Making a basic hello world app is as easy as making a simple web page. You can even do it straight from your browser! I recommend taking advantage of Firefox’s WebIDE to make firefox OS application building a breeze, at least at first. Simply press shift+F8, or … Continue reading


So far as I'm concerned, you write sane code, and you ask when you're stuck, and you listen to design ideas and then ask questions and then implement them.

Matt Trout, Shadowcat Systems Technical Director.

We get a lot of contributors but it is not every day someone so seamlessly integrates with the entire team. I went away on vacation and when I came back Errietta was an integral part of our work environment – a powerful presence on IRC, at our video demo call and on GitHub. I hope she continues to lend us her talents for a long time to come.

Cassie McDaniel, Webmaker UX Lead (Source)

Errietta has all the qualities of a great web developer in the making — she learns quickly, values feedback from both engineers and designers, and cares deeply about sharing her knowledge with others. I'm always impressed by how quickly she's willing to jump into a new code base and effectively solve problems.

Kate Hudson, Webmaker Developer