Harrison Deo

Harrison Deo · Senior Frontend Engineer · UK

I build products people actually use.

Over seven years shipping frontends, from fintech platforms to a browser extension thousands of developers rely on every day. Currently Frontend UI/UX Engineer at Silvercat.

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Selected work

Things I've shipped

Browser extension · 2023 to present

Flex Headers

  • 7,000+users
  • 4.9 ★Chrome Web Store
  • Chrome & Firefoxopen source

The existing tools for editing HTTP headers had become slow, bloated and, in one case, compromised. I built Flex Headers for my own day-to-day work: a free, lightweight, privacy-focused extension that does one job well.

It caught on. Three years later I still maintain it solo, answer every issue and email, and keep shipping features like cross-device sync and undo history.

Project page →Chrome Web StoreFirefox Add-onsGitHub
The Flex Headers popup: a Production page with three headers, one disabled, and a URL filter
Pitskill

Sim racing platform · co-built

Pitskill.io

A platform where sim racers find and compete in organised online events. I co-built it with one other developer; we were both full-stack, covering everything from the React frontend to the Azure infrastructure. I'm no longer involved day to day.

React · MaterialUI · Azure

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Travel planner · solo build

Plan Away

A travel planning app I designed, built and shipped end to end, from the interface to the backend and deployment. Still live, still running, and it taught me more about what makes a product stick than anything I've read.

Full-stack · solo

Visit site →

How I work

Agentic by default, accountable for every line.

I've rebuilt my workflow around agentic coding tools: Claude Code for personal projects, GitHub Copilot's agent mode at work. The tools changed; the standard for what ships didn't.

  1. Plan first. I write the spec and the constraints before any code is generated, and interrogate the plan harder than the diff.
  2. Delegate the draft, own the review. An agent writes most of the first pass. I read every line that ships, and I'm the one who answers for it.
  3. Spend the saved time on the product. Less boilerplate means more attention on the interface, the edge cases and the users.

The practical result: I maintain two live products solo, in the evenings, alongside a full-time role.

About

A frontend engineer who ships the whole thing.

I'm a senior frontend engineer based in the UK with over seven years in the industry. Since October 2024 I've been a Frontend UI/UX Engineer at Silvercat, a London fintech, building customer-facing and internal products that let the group's customers and employees do more for themselves. Before that I was a senior developer at Next, where much of my work was modernising the frontend architecture.

Frontend is the depth, not the limit. On my own projects I own the backend, infrastructure and deployment too.

Day to day: React, TypeScript, Next.js, Node, Playwright and Jest, CI/CD, Docker, AWS and Azure.

Away from the keyboard: racing, sim and real, and as much time outdoors as the UK weather allows.

Contact

Say hello.

Roles, collaborations, or a question about Flex Headers. I read everything.