Kirppu — Lead UI Design & Design System
As Lead UI Designer for Kirppu, Denmark's largest flea supermarket chain, I worked across multiple digital products — improving the Mit Kirppu seller app and designing a brand-new Showroom experience that brings second-hand treasures online. Alongside product work, I built Kirppu's design system from scratch to unify their growing digital ecosystem.
Role
Lead UI Designer
Client
Kirppu, Denmark
About Kirppu
Kirppu — meaning “flea” in Finnish — is Denmark's first and largest chain of indoor flea supermarkets. Inspired by the Finnish Kirpputori concept, Kirppu lets private sellers rent a stand, price their items, and set up their goods — while Kirppu staff handle the actual sales, checkout, and security. With 27+ stores nationwide and millions of unique second-hand items passing through their stores, Kirppu has reimagined circular shopping at scale.
Every item in a Kirppu store is unique, and the assortment changes daily as new stand renters move in. That makes the digital experience just as important as the physical one — sellers need tools to manage their stands, and buyers want to discover treasures before visiting the store.
Multiple Products, One Design Language
My engagement spanned several interconnected digital touchpoints. Rather than treating each as an isolated project, I approached them as parts of a single ecosystem — ensuring sellers and buyers experience a consistent Kirppu brand whether they're tracking sales on their phone or browsing the online showroom.
Mit Kirppu App
Seller companion · iOS & Android
The Mit Kirppu app (also known as Katjiing) is the primary tool for stand renters. Sellers use it to book stands, create digital price tags, track live sales, view payouts, and get notified every time an item sells — complete with the signature “Katjiing” sound.
- Redesigned core flows for stand booking and sales tracking
- Improved price tag creation and item labelling experience
- Refined navigation and information hierarchy for daily use
Kirppu Showroom
Online marketplace · kirppu.dk/varer
Showroom is Kirppu's online window into their physical stores. Buyers can browse thousands of unique second-hand items across categories — from fashion and home decor to electronics and hobbies — filter by store location, price, colour, and discount, then reserve items for click & collect or delivery.
- Designed the product browsing and filtering experience
- Created item detail views and reservation flows
- Built a favourites system for saving discoveries
The Showroom Experience
Showroom bridges Kirppu's physical stores and digital discovery. Because every item is one-of-a-kind, the interface needed to feel like browsing a treasure hunt — rich filtering to narrow down the hunt, but enough visual delight to make scrolling through loppefund genuinely fun.
Filters
Price
Find varer
Sukulent i ramme
45 kr.
Loppefund
120 kr.
Bolig & indretning
85 kr.
Building a Design System from Scratch
Kirppu's digital products lacked a shared visual foundation. Each surface — the app, the website, the new Showroom — had grown organically with inconsistent patterns. As Lead UI Designer, I took ownership of creating Kirppu's design system from the ground up.
Foundations
Defined colour tokens, typography scales, spacing units, and border radii — anchored in Kirppu's warm, approachable brand while meeting accessibility standards.
Component Library
Built reusable UI components — buttons, cards, form inputs, filters, badges, and navigation patterns — documented for designers and developers across all Kirppu products.
Layout & Grid
Established responsive grid systems and layout templates that work across the mobile app, web showroom, and marketing pages.
Cross-Product Consistency
Ensured the Mit Kirppu app and Showroom share the same visual language — so sellers and buyers recognise Kirppu instantly, whether on a phone screen or a browser.
What I Took Away
- Designing for uniqueness. Unlike typical e-commerce, every Kirppu item is one-of-a-kind. The UI had to embrace that unpredictability — making discovery feel exciting rather than overwhelming.
- Systems thinking at scale. Building a design system while actively designing multiple products taught me to make decisions that serve the ecosystem, not just the screen in front of me.
- Two audiences, one brand. Sellers and buyers have completely different needs, but both need to feel at home in Kirppu's digital world. Balancing those perspectives was central to every design decision.
Interested in working together?
Let's talk.
Give me a call, send an email, or reach out directly on LinkedIn — whichever works best for you.
