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.

05 PROJECTS

01IN PROGRESS / 2026

DevLinks

Developer identity platform.

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

DevLinks — developer identity platform interface
02IN PROGRESS / 2026

Vitta

Personal wellness tracker.

Stack / TanStack · Drizzle · PostgreSQL · PWA · Offline-first

Vitta — personal wellness tracker interface
03SHIPPED / 2026

Trace

Provenance-tracing tool that reconstructs where an article's claims actually come from.

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

Trace — provenance-tracing tool interface
04IN PROGRESS / 2026

WebDiff

Compares two versions of a webpage and explains what changed, in plain language.

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

WebDiff — webpage change diffing tool interface
05IN PROGRESS / 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

Build Status

Currently building.

DEVLINKS

Developer identity platform

80%
VITTA

Offline-first wellness tracker

90%
WEBDIFF

Webpage change diffing tool

70%
VITALGATE

Core Web Vitals performance guard

50%

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 shipping client-facing products 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

Tools I like

ReactNext.jsTypeScriptTanStackDrizzlePostgreSQLTailwindGodotCloudflareDockerGithub ActionsAWS

Build Log

What I've been doing.

  • 08.27.26Added new developer integrations
  • 08.18.26Vitta offline-first architecture
  • 08.14.26Built Korean photo strip maker
  • 08.06.26Reworked DevLinks profile editor
  • 07.29.26Shipped PawHome adoption flow v2