Product Management

Philipp, Lead Designer of Firefox, Talks Usability & Empathy

Published March 3, 2016 ⚡ Updated on October 2, 2023 by Markus Pirker
Philipp, lead designer of Firefox talks usability and empathy

A few weeks ago we met Philipp Sackl, the lead designer of Firefox at Mozilla, at the UX Day in Graz where he gave an inspiring talk about empathy and design.

He was talking about how startups are often solving first-world problems (or even non-problems), how our current service economy is driven by greedy folks trying to make billions, and how design is not on the side of users anymore, but on the side of investors having fever dreams of exponential hockey sticks.

Man, he was really opinionated about all this. Just as he’s opinionated about being a designer.

So if you care about design—and more importantly—people, you should really keep on reading to see what the lead designer of one of the most known and used pieces of software has to say about usability, design, and empathy.

What’s your job at Mozilla?

I lead the design team of Firefox desktop. In terms of what I actually do every day, it’s a mix of feedback/critique and design strategy. Sometimes I even get to design something myself!

How is your team at Mozilla set up?

The Firefox UX team includes interaction designers, visual designers, prototypers and researchers. For each project a hand full of us work together with engineers, product managers, program managers and QA engineers in cross-functional teams.

Interview Participant in Bangkok, Thailand
Image taken from Mozilla UX Blog

In your talks you often mentioned empathy being a key characteristic for UI/UX designers. Why is it important for a designer to be empathic?

As a designer, your entire job is anticipating what people will do and feel. The abundant availability of data that has shaped the industry in the past few years has made it really easy to know the »doing«-part, but I would argue that it has actually made it harder to reason about motivations and emotions.

There is this notion now that observing and understanding the individual is not quantitatively representative and therefore not useful. I couldn’t disagree more. Yes, working with individuals in qualitative studies and user tests won’t tell you whether to make the signup button red or green, but it will tell you a lot about what people could think and feel when clicking that button.

How do you make sure that Firefox, a browser with more than 400 million people using it, actually is usable?

There’s no silver bullet. Designing for a product of these proportions involves user research, data and a good portion of intuition. It also means accepting that most of the ideas that sound good in the beginning might be good for a portion of users, but not the entire Firefox user base. We often ship those features as add-ons or experiments in order to validate their fit for a larger audience.

In your experience, what’s the biggest advantage of watching people really use your software, instead of just analyzing quantitative data?

Both methods are useful and both methods provide different kinds of insights. Quantitative measurements are really good at telling you what people are doing. It can tell you whether solution A performs better than solution B given a specific measure. It will not, however, give you any insight into motivations, feelings, rationalizations and desires of a user.

An example of quantitative and qualitative research working iteratively.
Image taken from Mozilla UX Blog

Qualitative testing can also provide insights outside the system you’re actually working on. For example, we learned a lot about how people use hacks that involve lots of texting and emailing things to themselves during a research project about task continuity. We would have never gotten those insights by watching the metrics on Firefox Sync.

How often are you testing Firefox with real people?

We rarely test Firefox as a whole, but we do a lot of testing (mostly through remote user testing) of specific parts of the browser. One of our current projects for example is to improve the onboarding of new users into Firefox, so we are making lots of Chrome users install Firefox and look over their shoulder.

We are making lot's of Chrome users install Firefox and look over their shoulders. Click To Tweet

In addition, we also do field research periodically to expand our view on the problem space. Those field trips have triggered some of the most inspirational moments in my life.

How do you fit usability testing into your stressful working process?

We are fortunate enough to have a small but extremely dedicated and talented team of researchers at the Firefox UX team. That means that oftentimes, getting answers to a research question is as easy as asking.

In addition, most of the designers on the team have been doing some research themselves in the past, which makes it easier for them to test their concepts and ideas.

Firefox on Windows 10
Image taken from Mozilla UX Blog

Can you remember your last „Oh shit“ moment while watching someone testing Firefox?

A while ago, we realized that a surprising number of people weren’t able to find a bookmark just moments after saving it. We started some user testing and had for example one person who spent 2 minutes finding a bookmark right after saving it.

Firefox has around 400 million users. If every user encounters this scenario once, we have wasted more than 1500 years of human attention. That’s roughly 18 lifetimes, lost because of a flawed design. Some fixes for that problem are rolling out now.

How do you make sure that the issues uncovered during usability tests actually change to the better?

Mozilla is a company with very little hierarchy, so advocating for changes and projects that you care about is a critical skill. It also depends on the issue uncovered: Sometimes it can be fixed really easily with a few lines of CSS, sometimes it triggers a month-long design project followed by the same time of engineering.

Animated mockup showing Firefox UI for TVs
Image taken from Mozilla UX Blog

What is your biggest challenge at Mozilla, when it comes to usability testing?

The sheer scale of the product. At 400 million users, it is guaranteed that every change will improve somebody’s workflow and completely destroy someone else’s. So there’s always a lot of interpretation and guesswork involved when looking at test results. It also means having to watch your own biases more closely.

Do you have any insight for people, who are just starting their careers as UI or UX designers?

When starting a career, it can feel like others have figured out the »right« way to do things. Rest assured that they are winging it just as much as you are. We just got more confident about improvising.

What’s currently on your bookshelf?

I’m currently reading the journals of artist Keith Haring. It’s a very weird mixture of musings about art, philosophical explorations and anecdotes about his life.


Philipp SacklPhilipp is the lead designer of Firefox at Mozilla. That means he spends a lot of time thinking about browsers so that you don’t have to. Prior to that, he’s been a co-founder of the design agency envis precisely and an interaction designer at BMW. He enjoys good food, good beer and bad jokes.

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