
Mac Kozal
Verified Expert in Design
Designer
Barcelona, Spain
Toptal member since December 23, 2019
Mac is a freelance product design lead with 15+ years of design experience across product design, UX, and architecture. He specializes in complex software platforms, B2B products, internal tools, and 0-to-1 systems. He works deeply embedded with client teams, shaping UX strategy, workflows, design systems, analytics, and AI-assisted prototyping. Teams he has worked with in the last five years have raised $320+ million.
Portfolio
Work Experience
Product/UX Designer
Freelance Projects
- Designed a tool that helps you understand and improve your company's entire people's experience.
- Conducted multiple iterations and user tests for the tool mentioned above.
- Used feedback from user testing and multiple iterations and chose the best solution to make an overview homepage with a top-level interactive chart with filterable information, benchmark data, and real insights.
- Worked with an alternative data provider, offering European point-of-sale transaction data. The company gathers non-personal data from new or hard-to-access sources, combining vast amounts of information into fast and reliable intelligence.
- Helped the alternative data provider update their landing page to communicate their value proposition better and made a set of interactive diagrams that made it easier to convey that message.
- Collaborated with the technical services company in the telecommunications and utility industries that has 1,000 employees, providing outside and inside plant design, planning, project management, inspection, RBOCs, ILECs, CLECs, IXCs, and so on.
- Designed an advanced web-based utility tool for the company mentioned above that manages field data collection projects in remote and urban locations (data-heavy project).
- Created the design for the user interface and UX of the data input, data management, and presentation and oversaw the UI/UX of GIS data.
- Designed an advanced web-based tool that solves molecular reactions and chemical problems using multiscale methods to simulate a small, chemically important region or a larger, complex chemical environment.
- Designed the marketing webpage, technical documentation, logo, and branding elements.
Lead Product Designer
TakeUp LLC
- Served as a product design lead and a long-term embedded design partner to the founding team, product, engineering, data science, CS, and leadership.
- Shaped the product experience at a strategic and systems level: clarifying ambiguous product problems, defining UX direction, translating complex pricing logic into usable workflows, and raising the quality bar.
- Led design across core product areas, including rate management, pricing controls, forecasting, reporting, competitor insights, and decision-support tools.
- Made AI-driven recommendations understandable, trustworthy, and actionable for non-technical hospitality operators.
- Designed functionality that reduced manual rate overrides by up to 80%, helping customers rely more on automated pricing while keeping control.
- Owned product analytics across PostHog, Mixpanel, and Hotjar, connecting user behavior, product friction, and design decisions.
- Used AI throughout the design process for research synthesis, UX logic exploration, interface ideation, microcopy, documentation, QA support, and faster iteration.
- Proposed an AI-driven prototyping workflow where design, production code, and AI-generated prototypes used the same design system.
- Contributed to venture-backed product work, which raised an $11-million Series A.
Lead Product Designer
1848 VENTURES LLC
- Served as a product design lead at a venture studio. Worked as an embedded design partner for the founding team, product, engineering, data, operations, customer-facing teams, and leadership.
- Led design across complex B2B and AI-enabled products, shaping workflows where users needed to understand data, make decisions, configure rules, review recommendations, and act with confidence.
- Helped early-stage and growth-stage products move from ambiguity to structured product direction, with a focus on UX strategy, systems thinking, and high-quality execution.
- Translated complex business logic, automation, and domain-specific workflows into clear, usable product experiences.
- Contributed at strategic and execution levels: clarifying product problems, defining UX direction, designing core workflows, creating scalable interaction patterns, improving interface quality, and helping teams make better product decisions faster.
- Worked closely with product analytics and user-behavior tools to connect design decisions with real product usage, friction points, adoption patterns, and opportunities for improvement.
- Made AI a part of my design workflow for research synthesis, UX exploration, interface ideation, microcopy, documentation, QA support, and faster iteration.
- Explored AI-assisted prototyping workflows, where design systems, production components, and generated prototypes could become more closely aligned.
Product Designer
Thinking LSAT LLC
- Worked as an embedded product design partner for LSAT Demon, contributing to a mature LSAT learning platform with dense educational content, adaptive study logic, and complex cross-device student workflows.
- Partnered closely with the founder and content creator to translate expert teaching models into clear product structures, helping bridge educational strategy, student behavior, and interface design.
- Designed core logged-in experiences across web and mobile, including student dashboards, lesson flows, and drilling interactions, with a focus on clarity, consistency, and learning momentum.
- Simplified complex LSAT preparation workflows into minimal, intuitive product experiences without reducing the depth required for serious test preparation.
- Helped shape ambiguous product problems into coherent design directions by clarifying user flows, interaction models, information hierarchy, and reusable UX patterns.
- Contributed to a high-maturity product environment where the design mandate was strategic refinement: improving coherence, usability, and visual quality in an already strong platform.
Product Designer
Intelligent Hotel Operations System Company
- Helped the client by designing a product that allows for the design and operation of building infrastructure systems so they can be net-zero (carbon neutrality).
- Collaborated with product managers and software developers in Agile development teams to gather and evaluate online platform user requirements.
- Illustrated and presented design ideas using storyboards, sitemaps, and process flows.
- Designed and defended graphical user interface (GUI) elements conforming to best practices for style, fonts, colors, and images.
- Developed UI mockups and prototypes for the platform's appearance and user experience.
- Troubleshot and identified UX problems such as intuitive operation and responsiveness.
- Ran design discovery and delivery phases for the design phase.
Data Visualization Designer
Open Ocean UK LLP & Saïd Business School - University of Oxford
- Conceptualized and designed an interactive data visualization system and dashboards for a venture classification platform. It uses artificial intelligence to classify startups, building insight into businesses and their underlying technology.
- Worked on the design discovery and delivery phase, including data research, choosing the best plotting methodology, and interactive maps.
- Collaborated closely with data scientists and developers to ensure the solution was feasible to develop.
Product Designer
Iambic Therapeutics, Inc.
- Designed complex scientific software, contributing to an AI-driven drug discovery platform spanning molecular design, biochemical experimentation, compound management, assay workflows, and structure-based drug design.
- Contributed to expert R&D workflows where scientists needed to design experiments, manage compounds, analyze molecular and biochemical data, interpret assay results, and turn experimental outputs into research decisions.
- Designed an advanced web-based molecular utility tool for calculating and comparing molecular properties, exploring reaction pathways, measuring bonds and angles, editing geometries, and exporting scientific images and videos.
- Translated dense scientific processes into clear product structures, interaction models, and data-oriented interfaces without oversimplifying the biochemical and computational logic behind the workflows.
- Designed high-throughput experimentation tooling (HTE) to support experiment planning, structured data capture, analysis, and iterative discovery cycles.
- Improved UX for compound and assay management by clarifying information architecture, reducing workflow friction, and strengthening consistency across data-heavy scientific interfaces.
- Contributed to structure-based drug design workflows by making complex molecular, target, and experimental data easier to navigate, compare, and act on.
- Brought product design structure to ambiguous scientific R&D problems, turning highly technical requirements into usable, scalable web-based tools for expert users.
- Worked within a high-growth AI drug discovery company backed by major funding rounds, including a $53 million Series A, $100 million Series B, $50 million Series B extension, and over $100 million in additional oversubscribed financing.
- Contributed to the design of a laboratory information management system (LIMS) to enable seamless integration of AI/ML-assisted predictions with highly automated wet lab processes.
Product Designer
Entos
- Designed from scratch an advanced web-based utility tool that calculates and compares molecules' properties, explores reaction pathways, measures bonds and angles, edits geometries, and exports images and videos.
- Handled the tool's design discovery and delivery phases.
- Delivered ideation sketches and explorations, workshops, user flows, wireframes, information architecture explorations, low- and high-fidelity prototypes, iterative updates design, motion design, documentation, design system, and webpage design.
Lead Product Designer
Mitel
- Led the design improvements of multiple service delivery portals that cross the hardware and software set up. I turned large, complex admin environments into easy-to-use yet functional design solutions.
- Worked collaboratively with stakeholders, domain experts, and partners while driving to a goal. I defined the service delivery design, user flows, and journeys.
- Contributed to the company road map and worked on quick wins, scoping out needs for longer-term strategies.
- Collaborated with different teams simultaneously on multiple enterprise-level UX experience projects in parallel: complex administration flows, very high-level UX, interaction design, order management system, shopping cart, etc.
- Handled billing-related experiences, dashboarding, workflow builders, CX admin tools, and app store design.
- Handled the company's design system. Collaborated with a dedicated development team and external specialists to ensure the system's quality.
- Handled the PBX configuration portal and outlined the experiences that enable hardware set up through the software.
- Handled the redesign of the CC tool and worked closely with PLMs on various user experience improvements.
- Contributed to the Mitel analytics program, defined the scope of the MVP from the user experience perspective, and embedded the external business intelligence tool (including making the working prototypes with the dummy data I prepared).
- Performed multiple studies and research exercises that led to product improvements.
UX/UI Designer
Byers Engineering Company
- Helped the client with the design of an advanced web-based utility tool that manages field data collection projects in both remote and urban locations.
- Assisted the client in making the tool for disconnected and connected data points in an easy-to-use, short lead time deployment scenario for locational accuracy and situational awareness.
- Worked on the discovery and delivery phases, wireframes, prototypes, user tests, and design documentation.
UI/UX Designer
True Footage
- Conceptualized the design of a real estate web app for Mac that allows drawing floor plans.
- Prepared a library of building-related equipment assets that users can use in their floor plans.
- Adjusted the app to the new version of Apple's human interface guidelines.
Product Designer
Starred.com
- Designed and framed the design for the development process.
- Constructed and maintained a scalable design system: Polestar.
- Built the data-informed culture within the organization by implementing tools like Mixpanel and Hotjar.
- Applied UX methodologies to a survey that improved the completion rate by 51-95%.
- Worked on the UX platform and various UI improvements.
- Prepared and performed usability tests and conversations with users.
- Developed a feature prioritization methodology that helped us address problems better.
- Conceptualized and designed Starred Connect from scratch; It is part of the platform that allows building integrations with external apps without code knowledge. The average time to integrate with other platforms decreased from days to minutes.
- Designed Template Gallery and Insights Gallery, tools that allow our users to improve the UX for the respondent and achieve better, more actionable insights.
- Evangelized design-driven processes within the company.
Co-founder | UX/Product Designer
Mood Tracker
- Conceptualized and designed the mood tracker iOS/Android app; it was developed using React Native, Expo, and TypeScript.
- Managed the project and remote developer who helped to build it.
- Designed and maintained the design and animation system.
- Prepared and managed the design and motion documentation.
- Experimented and developed new features and proposed improvements from user feedback.
Product Designer
Suburbia
- Created the user experience for the product and landing pages.
- Designed and prototyped interactive charts and diagrams.
- Developed the strategy for iterative future changes for the landing page.
Co-founder | UX/Product Designer
Games Tracker
- Conceptualized and designed an online tool for tracking your computer games history.
- Designed and maintained the design system for the dark UI.
- Prepared the documentation, experimented with, and developed new features.
- Supervised the project and managed a remote developer.
Co-founder | UX/Product Designer
Coypu
- Conceptualized and designed an ext-editor-like weekly planner.
- Prepared comprehensive documentation, overseeing and scoping the project for its MVP stage.
- Managed a remote developer. Performed user testings, experimented, and developed new features.
Co-founder | UX/Product Designer | Content Creator
Echotags
- Conceptualized and designed hands-free: an offline audio guide to Amsterdam app (native iOS).
- Prepared the market research and created and implemented usability tests.
- Prepared the documentation and supervised the project.
- Managed a remote developer. Performed usability heuristics and user testings. Experimented and developed new features.
- Prepared the content and organized voice recordings for over 200 points of interest (POIs).
- Designed the data organization structure, made the illustrations for the landing page, and prepared a comic-style newsletter for the users.
Architectural Designer
Multiple Companies
- Acted as an architect and architectural designer for multiple companies in different countries.
- Advised clients in the whole spectrum, from interiors to urban design, based on solid knowledge of engineering, construction, and regulations.
- Drove design explorations and crafted comprehensive design documentation for multiple projects.
Co-founder | UX/Product Designer
Jottings
- Conceptualized and designed a real-time collaborative text editor in Markdown. Prepared the documentation, supervised the project, scoped it for MVP, and performed user testings.
- Handled both the discovery and delivery phases of the project.
- Experimented and developed new features for the project roadmap.
Co-founder | UX/Product Designer
Checkers
- Conceptualized and designed Checkers for iMessage: a board game for iOS 10 iMessage and Native iOS app, one of the first iMessage apps on the market promoted by Apple with over 140,000 users.
- Managed the project and a remote developer. Prepared the documentation.
- Performed usability heuristics and user testings. Experimented and developed new features.
Education
Master of Architecture Degree in Architecture and Urban Planning
Lodz University of Technology - Łódź, Poland
Skills
Tools
Hotjar, Atomic.io, Marvel, InVision, Balsamiq Mockups, Lucidchart, UsabilityHub, Maze, SketchUp Pro, Sketch, Flinto, Jira, Google Analytics, Procreate, GIS, Web GIS, Proto.io, ProtoPie, Principle, Adobe Photoshop
Platforms
Figma, iOS, MacOS, Android, Windows, Mixpanel, Adobe Suite, Web, Mobile
Industry Expertise
Architecture, Healthcare, Human Resources (HR), Psychology & Mental Health, Health & Wellness
Languages
HTML, CSS
Other
Web Applications, Usability Testing, Design, Software, Low-fidelity Prototypes, System Design, Feature Prioritization, UX Assessment, UX Wireflows, Component Libraries, UI Components, Personas, Web App UX, Web App UI, Web App Design, Mockups, Complex Application User Interfaces (UI), Complex Web Systems, UX Design, UI Design, Digital Product Design, WebApp, Mobile Apps, Dashboards, Design Systems, Analytics, User Testing, SaaS Design, Concept Sketching, Ideation, Pen & Paper, Pencil Drawing, Low-fidelity Mockups, High-fidelity Mockups, High-fidelity Prototypes, Data Visualization, Flowcharts, UX Flows, User Flows, User Paths, Surveys, Form Design, Documentation, UX Documentation, Presentation Boards, Graphic Presentations, Visual Design, Visualization Design, Information Visualization, Prototyping, UX Analysis, Wireframing, Information Architecture (IA), Design Documentation, Product Design, Consumer-facing Product Design, User Experience (UX), Software Design, User Interface (UI), User Research, Web Design, Agile, B2B, Dashboard Design, User Journeys, Lean UX, Complex Problem Solving, User-centered Design (UCD), UX Strategy, Responsive Web Design (RWD), Responsive Web Apps, Journey Mapping, UX Architecture, UX Audits, App Design, Data Architecture, Web UI, Web UX, Web UX Design, User Stories, Competitive Analysis, Management Systems, Product Consultant, Consulting, Enterprise SaaS, Mobile Design, UX Principles, Design Leadership, Design Guidelines, Interaction Design (IxD), UX Wireframes, Style Guides, Best Practices in Design, Analytical Dashboards, Key Performance Indicators (KPIs), B2C, B2B2C, Collaboration, Enterprise, Leadership, Mobile UX Design, Mobile UI Design, Commercial Real Estate, Residential Real Estate, Real Estate Development, Layout Design, Remote User Testing, Business to Business to Consumer (B2B2C), Workflow, Interactive UX, Interactive UI, UI Maps, Maps, User Journey Maps, Enterprise Application Design, Enterprise Systems, User Workflows, AI Design, Design Strategy, Data Analytics, Customer Journey, Database as a Service (DBaaS), Product Growth, Mobile UI, User Validation, Heuristic Evaluation, Usability, Heuristic Analysis, Artificial Intelligence as a Service (AIaaS), Product Research, Qualitative User Research, Quantitative User Research, SaaS, Illustration, Strategy, User Metrics, Presentation Design, Data-informed Visual Design, User Personas, Brainstorming, Empathy Mapping, Strategic Design, UX Research, Websites, eCommerce UI, eCommerce UX, eCommerce, Medtech, Content Management Systems (CMS), Enterprise Design, Scheduling Tools, 3D Architecture, Marketplaces, WCAG 2, Big Data, Financial UX, Qualitative Research, Quantitative Research, Conversion Rate, Architectural Design, Abstracts, Design Sprints, Atomic Design, Google, Computer Automation Design (CAD), DataViz, Charts, Data, Video Presentations, Recruitment, Emojis & Emoticons, Emotional Design, Dark UIs, Apps, Research, Metrics, Survey Design, Corporate, Recruiting, Customer Service, Surveying, Online Surveys, User Surveys, User Interviews, Concept Testing, User Preferences, Remote Usability Testing, Heatmaps, Quality Assurance (QA), Motion Design, Task Flows, Audio Montage, Hand-drawn Illustrations, Vector Art, Content Marketing, Content Creation, Newsletter Design, Mobile GPS, Geolocation Detection, Geolocation, High-speed Design, Tourism, Landing Page Design, Newsletters, User Feedback, HR Tools, User Permissions, User Profiles, Line Drawing, Hand Drawing, Digital Drawing, Material Design, Geography, Geographic Information Systems, Forms, 3D, Microinteractions, Video Post-production, Design Workshops, UX Leadership, Testing, Accessibility, Web Accessibility, Admin Panels, Admin Support, UX Workshops, Hardware Design, Landing Pages, Corporate Design, Multidisciplinary Design, Branding, Fintech, App UX, App UI, Interactive Charts, Information Design, Data Collection, Web Forms, Applications, Event Coordination, Electric, Enterprise System Design, Enterprise Software, AI-assisted Design, Front-end, Product Strategy, Web Platforms, User Experience Design, User Experience Strategy, CRM, Web Analytics, Pricing, AI Agents, PostHog, Dynamic Pricing, Pricing Models, Customer Experience (CX) Design, Focus Groups
Experience
- User Research - 14 years
- User Experience (UX) - 14 years
- Ideation - 12 years
- Web Design - 7 years
- Digital Product Design - 7 years
- User Interface (UI) - 7 years
- User Testing - 7 years
- Design Systems - 2 years
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