Jonathan Zielenkievicz
A New York City Based Senior Web Developer
I create responsive, full-stack, accessible, search engine optimized websites.
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About
I'm a Senior Web Developer with over 15 years of experience building high-quality, performance-optimized web solutions. I specialize in fast, accessible, full-stack websites — including healthcare and pharmaceutical platforms built to perform within strict regulatory and legacy-system constraints, where I've pushed Lighthouse scores to 90+ across production deployments.
I'm proficient in HTML5, CSS3, JavaScript, and modern frameworks, and I lean on creative and critical thinking to solve hard problems and deliver engaging, interactive websites.
For a full list of my professional work history, see the experience section below. For examples of sites I've designed, developed, and built, checkout my personal projects.
Skills
Frontend & Performance
Technologies & Tooling
Experience
Senior Web Developer
2020 — 2025
Interpublic Group
- StudioRx (2023-2025)
- Craft Worldwide (2022-2023)
- Freelance Consultant (2020-2022)
Built and maintained healthcare-provider-facing pharmaceutical websites, web apps, banners, and HTML emails within regulated environments; delivered 20+ production sites and pushed Lighthouse scores to 90+ across deployments while writing high-quality, maintainable code in a fast-paced work environment.
Front End Web Developer
2015 — 2020
NYC Tourism + Conventions
Maintained and assisted with upgrades to the Official Visitor's Guide to New York City, which was visited several thousand times daily; rebranded signature marketing programs (e.g., Broadway Week, Off-Broadway Week, Restaurant Week) and other initiatives that helped NYC tourism grow from 54 million visitors (2014) to over 66 million visitors (2019); proposed and implemented new technologies to improve front end development, performance, and speed.
Web Developer
2014 — 2015
Fly Communications
Worked with designers and project managers to create dynamic, optimized websites that met client needs and were aesthetically pleasing; built tailor-made websites for nationally recognized brands; updated legacy code using graceful degradation for older web browsers; researched the latest developments with web technologies and incorporated best practices.
Jr. Web Developer
2009 — 2013
Sanky Communications
Built custom websites, landing pages, HTML emails with cross-browser/platform compatibility for nationwide nonprofits; gained proficiency in multiple client CMS platforms; led account teams on SEO techniques, resulting in top rankings for keywords.
Projects
5 Points Foundry
A one-person web studio built to help NYC small businesses grow online with professional websites, care plans, and hands-on support from an actual neighbor.
The Free Banano Faucet
A full-stack cryptocurrency faucet that has handled 84,000+ claims and distributed 3,600+ BAN. Get free Banano sent to your wallet, see Banano's USD price, and learn about the Banano cryptocurrency.
Change Word Case - An Online Case Converter
An online case converter with 1,000+ organic search impressions. Quickly change word case and convert text to: upper, lower, title, alternate, kebab, pascal, camel & snake case.
Zielenkievicz.com
The portfolio site for Jonathan Zielenkievicz, where you can learn about my work experience, personal projects, skills and a little about me.
