Francis Castillo

Francis Castillo — Frontend Developer

I builddigital thingsworth using.

I design and build interfaces, products, and experiments — from idea to implementation. Frontend developer & product builder based in the Dominican Republic.

Available for selected projects

Selected Work

Things I've shipped.

07 PROJECTS

01SHIPPED / 2026

Palabreo

Wordle in Spanish, with a daily challenge, timed and hard modes, and weekly leaderboards.

Stack / TanStack Start · React · Drizzle · PostgreSQL · Better Auth

Palabreo — Spanish Wordle game board with on-screen keyboard
02IN PROGRESS / 2026

DevLinks

A developer profile in one link: GitHub activity, articles and projects synced automatically, with a theme builder and cookieless analytics.

Stack / TanStack Start · React · Drizzle · PostgreSQL · Better Auth

DevLinks — developer identity platform interface
03IN PROGRESS / 2026

Vitta

Log your weight in five seconds and track water, steps, sleep and measurements, with an estimated goal date and 30-day trends.

Stack / TanStack · Drizzle · PostgreSQL · PWA

Vitta — personal wellness tracker interface
04SHIPPED / 2026

Trace

Paste a URL and Trace reconstructs where an article's claims come from: what it cites, what copies it, and where each claim first appeared.

Stack / TanStack Start · React · Drizzle · PostgreSQL · Better Auth

Trace — provenance-tracing tool interface
05SHIPPED / 2026

WebDiff

Compares two versions of a webpage and explains what changed in plain language — content, visuals, structure and metadata — and can watch a URL for changes.

Stack / TanStack Start · React · Drizzle · PostgreSQL · Better Auth

WebDiff — webpage change diffing tool interface
06SHIPPED / 2026

Vitalgate

Runs Lighthouse on every Pull Request, compares performance against your baseline, and blocks merges that fail Core Web Vitals.

Stack / TanStack Start · React · Lighthouse · GitHub Actions · Core Web Vitals

Vitalgate — Core Web Vitals performance budget tool interface
07SHIPPED / 2026

Nephrite

Low-glare jade color theme for Chrome, Firefox, VS Code and seven terminals: Windows Terminal, iTerm2, Alacritty, Kitty, Ghostty, Warp and WezTerm.

Stack / Chrome · Firefox · VS Code · Terminals · Design tokens

Nephrite — jade color theme for browsers, editors and terminals

Build Status

Currently building.

DEVLINKS

Developer identity platform

80%
VITTA

Weight and habit tracker

90%

Lab / Experiments

A running notebook.

About

Francis Castillo.

Frontend developer & product builder based in the Dominican Republic.

I enjoy turning ideas into useful products, interfaces and experiments — the kind of work that sits somewhere between engineering, product design and curiosity.

Most days I'm split between client work — like Deportes247, a sports news site for the Dominican Republic — and building small tools for myself, just to see if an idea holds up once it's real.

Focus

  • Frontend
  • Product design
  • Developer tooling
  • Creative experiments

Currently

  • Building
  • Learning
  • Experimenting

GitHub Activity

2,356 contributions / last year

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Tools I like

ReactNext.jsTypeScriptTanStackPayloadDrizzlePostgreSQLNeonBetter AuthTailwindMotionVercelCloudflareDockerGitHub Actions

Build Log

What I've been doing.

  • 10.08.26Added stats to Palabreo
  • 10.07.26Built Deportes247, a sports news site
  • 10.01.26Improved SEO, accessibility and docs on World Seed
  • 09.24.26Hardened DevLinks security
  • 09.20.26Built Could I Live There?, a city budget checker