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Sean Guillermo.
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Tools & platforms: Google, Google Ads, Semrush, Shopify, WooCommerce, Amazon, WordPress, Webflow, Next.js, React, Vue, TypeScript, Tailwind CSS, Node.js, Vercel, Cloudflare, Python, n8n, Make, Zapier, GoHighLevel, OpenAI, Claude (Anthropic), Google Gemini, Figma, GitHub, Sanity

GHL
GHL
Sean Guillermo Logo
Sean Guillermo.

Global performance agency engineering revenue-generating ecosystems through search science, psychological UI/UX, and architectural dominance.

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HomeServicesApp & Web Development
Engineering & Product

High-performance apps and sites built to convert

Custom web applications and conversion-focused sites built on Next.js and React — fast, accessible, SEO-ready, and engineered to scale with your business.

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100
Lighthouse performance score
100

Lighthouse performance

<1s

Time to interactive

+44%

Conversion vs. old site

AA

WCAG accessibility

What's Included

A website should be your hardest-working asset, not a brochure. I build fast, accessible, search-ready web applications and sites on a modern stack — engineered for performance, conversion, and easy content management down the line.

Next.js & React Apps

Server-rendered, type-safe applications built for speed, SEO, and maintainability.

Headless & Commerce

Headless CMS and commerce architectures that decouple content from presentation.

Conversion-Focused Design

Interfaces engineered around trust, clarity, and action — not just aesthetics.

Performance Engineering

Core Web Vitals, edge rendering, and image optimization baked in from day one.

Accessibility

WCAG-compliant builds that work for every user and protect you legally.

CMS Integration

Sanity, headless WordPress, or custom CMS so your team can publish without a developer.

What You Get

  • Custom Next.js / React application or site
  • Responsive, accessible UI system
  • CMS integration for self-serve content
  • Performance and SEO optimization
  • Analytics and conversion tracking
  • Documentation and handoff

Tools & Stack

Next.js React TypeScript Tailwind Sanity Vercel

How It Works

01

Discover & Architect

Define goals, map user flows, and design the technical architecture.

02

Design & Build

Build the interface and application logic on a modern, scalable stack.

03

Optimize & Test

Tune performance, accessibility, and SEO; test across devices.

04

Launch & Support

Ship to production, wire up analytics, and hand off with documentation.

Frequently Asked Questions

Do you design as well as build?

Yes — I handle design and engineering together, so the interface is both beautiful and built to convert.

Can my team update content ourselves?

Yes. I integrate a CMS (typically Sanity) so non-technical team members can publish and edit without touching code.

Will the site be SEO-ready?

SEO is built in — server rendering, clean markup, structured data, and performance are part of the build, not an afterthought.

Related Insights

AI & Development

Why I Build on Next.js: Speed, SEO, and Conversion by Default

A website should be your hardest-working asset. Here is why Next.js and a modern stack deliver the performance, search-readiness, and conversion edge that page builders cannot.

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Vibe Coding Is Here: Why Natural Language Programming Is Eating Traditional Dev

Vibe coding — using natural language to direct AI to write software — is not a parlor trick. Real productivity data shows it is reshaping how software gets built and who can build it.

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AI News

The Multimodal Explosion: How Vision-Language Models Are Changing Product Development

Vision-language models in 2026 can generate UI from screenshots, extract data from complex documents, and understand video — capabilities that are reshaping how product teams build and ship.

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Explore Other Services

Workflow & AI Automation

Automation & Integrations

Workflow automation, API integrations, and AI agents that connect your tools, eliminate manual work, and let your business run while you sleep.

Revenue-Focused Commerce

E-Commerce Growth

End-to-end e-commerce growth — product SEO, conversion rate optimization, and merchandising — that lifts revenue per visitor and lowers customer acquisition cost.

Organic Growth Engineering

SEO Optimization

Full-funnel search engine optimization — technical foundations, content authority, and link equity — engineered to put you on page one and keep you there.

Ready to get started with App & Web Development?

Book a free 30-minute audit. I'll map your biggest opportunity and send a custom plan within 24 hours — no obligation.

Book Your Free Audit