Robokiller - launching a strong product and scaling it to 1+ million paid customers

Mobile App Design
Growth Optimisation


  • FTC Robocall Challenge award in 2015 for the prototype
  • → Technology that reliably blocks spam calls
  • → Getting ready to launch a beta version of product to paid customers

With Lumi:

  • → Co-designed & co-managed a high-growth iOS app over the period of 2016-2018
  • → Reached 1,000,000 paid subscribers on iOS and awarded App of the Day feature
  • → Acquired by IAC in November 2018
It's estimated that people in the United States receive 190 million spam and robocalls per day. Robokiller’s team became aware of the problem through their other apps, like TrapCall & TapeACall, and had the groundbreaking technology to solve it.
We worked on Robokiller from its inception in 2016, through the incredible growth period that led to the acquisition of the whole company by IAC in 2018.

Designing a simple interface for a complex product

It’s the first impression that makes or breaks a product. In Robokiller’s case, the first few steps of the setup on the user’s part were complex and confusing to understand. Plus, they varied depending on your phone, network and even the version of your a phone system! Our goal was to remove the countless points of friction and have a systematic way to improve on all the things that could go wrong in the process.

Enabling & maintaining growth through design

The team established highly effective, data-driven processes to measure customer satisfaction, product improvements and growth. With each iteration, the product kept getting more functional, stable and better rated on the App Store. With product-market fit achieved, our focus shifted to empowering the growth team. The app was shipped quickly, so there was a lot of space for improvement. We focused on answering their questions on acquisition - how do we make the purchase decision as easy and effortless as possible for the users? And retention - how do we provide continuous value in what essentially was a 'set-and-forget' app?
Nicolo Luti founder of DiscoEat
Ethan Garr
Senior VP of Product, RoboKiller
With our focus on innovation, it was great to work with Lumi, who brought a design thinking approach to product ideation and design. They know how to create great products that make an impact, and it shows in all elements of their work.
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Intuitive product with a strong product-market fit

As a result of close collaboration with the development, product and growth teams at Robokiller, we created a maximally simple, intuitive experience that allowed people to receive all the benefits of spam protection in just a matter of minutes.

We also designed an innovative feature called Answerbots. Robokiller's system intercepted and answered calls from spammers and then played custom pre-recorded messages to them. These could be anything, from a simple 'number disconnected' message to someone having a full-on family meltdown. Then the app recorded the spammer's reaction to the message - which was often so hilarious that the users kept coming back just to listen to it. We pushed for simplicity - letting the user know when they got a new recording, but not making a big deal of the feature until we knew we had a really good one for them. 

That simplicity was exactly the source of success. The technology worked its magic in the background. The app didn't have a learning curve, there was nothing to remember. Users could simply enjoy a life without spam calls.

Breakout growth supported by design

Our starting point for growing Robokiller was to address all the points of friction - places in the experience where users got stuck, lost interest, or left the product dissatisfied. With thousands of new users trying the product every day, we continuously ran tests and brought in improvements methodically. Working closely with the data and development team, we connected design elements with user actions, mapping out the whole experience. This gave a very strong case for investing in better design to empower growth.
Most people in North America experience spam calls every day. Which means... literally everyone was in Robokiller’s demographic. Our focus quickly became about making the experience as straightforward, simple and joyful as possible to satisfy varying customers.
The key point of that was our user's first experience with the product - when they made the purchase decision and set up Robokiller protection. Making this process simpler and faster had a huge impact on the business, with individual tests resulting in up to a 10-20% improvement in conversions.
The main lesson we drew from working on creating & improving Robokiller was this: whenever we made a change that was showing users more value and quicker – it had a positive impact on the business.
This became our guiding principle and one we now evangelise in Lumi.

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