Frontend Engineer
Position: Frontend Engineer
Type: Freelance Hourly Contract
Compensation: $90/hour
Location: Remote
About the Opportunity
This opportunity is for experienced Frontend Engineers and Full-Stack Developers interested in evaluating AI-generated web interfaces and code.
The work focuses on comparing AI-generated frontend implementations against real-world reference websites, assessing both visual fidelity and underlying code quality .
This is an evaluation-focused role rather than a traditional development position. The key requirement is the ability to identify how a webpage is constructed, recognize technical shortcuts, and provide precise, evidence-based evaluations.
What You'll Do
Render a reference webpage and two AI-generated implementations at a 1920×1080 viewport and evaluate which version most accurately reproduces the reference.
Compare visual fidelity across different interface states, including layout, spacing, typography, colors, borders, images, layering, and overflow behavior .
Review the source code of AI-generated implementations and assess HTML structure, CSS architecture, responsiveness, maintainability, and implementation quality .
Identify technical shortcuts such as excessive hardcoded positioning, unnecessary absolute positioning, poorly structured markup, or image-based recreations.
Test responsive behavior across different viewport sizes and identify layout or usability defects.
Use browser DevTools to inspect elements, computed styles, DOM structure, and interactive states.
Provide specific, evidence-based written justifications explaining why one implementation is stronger than another.




Identify genuinely broken evaluation tasks while distinguishing them from tasks that are simply challenging.
Required Qualifications
3–8 years of professional web development experience , primarily in frontend or full-stack engineering.
Strong hands-on experience with HTML, CSS, JavaScript, responsive web development, and modern frontend engineering practices .
Deep understanding of semantic HTML, Flexbox, CSS Grid, media queries, and responsive layouts .
Ability to read and understand both modern and legacy web layouts , including float-based and table-based designs.
Strong proficiency with browser Developer Tools , including DOM inspection, computed styles, viewport testing, and interactive state debugging.
Comfortable working from the command line, including extracting archives, running local development servers, and troubleshooting asset paths .
Sufficient JavaScript knowledge to understand how scripts interact with the DOM and user interactions.
Strong professional written English and the ability to provide clear, detailed technical justifications .
Strong attention to detail and the ability to identify subtle visual and structural differences.
Preferred Qualifications
Prior experience with RLHF, preference labeling, AI model evaluation, structured code review, or human-feedback projects .




Pixel-perfect design-to-code experience, including work with design systems, templates, or production web interfaces .
Knowledge of web accessibility , including ARIA, semantic landmarks, and heading hierarchy.
Familiarity with common failure patterns in AI-generated frontend code .
Experience with web scraping, website archiving, DOM parsing, or working with complex crawled website structures .
Previous experience completing AI evaluation projects and working in multi-hour evaluation sessions.
Equipment Requirements
Desktop or laptop capable of displaying a 1920×1080 viewport .
Ability to run a local development environment and static web server .
Administrator access to your own computer for installing required development tools.
Important Project Requirements
Each evaluation unit typically takes 2–3 hours and is completed within a defined time window.
This is not microtask work and requires the ability to dedicate uninterrupted blocks of time to individual evaluations.
A functioning local development environment is required.
The role is intended for practicing web developers with strong frontend and UI implementation expertise.
Backend-only, ML/data-science-only, mobile-native-only, and DevOps-only backgrounds are generally not suitable for this evaluation work.
Compensation
Competitive compensation of $90/hour.
Independent contractor engagement.
Compensation is based on completed evaluation work in accordance with project requirements.
Application Process
Easy Apply on LinkedIn
Check Email for Next Steps
Participate in Resume Evaluation & Interview Stage

📌 Frontend Engineer (Remote | Up to $90/hr) (Valencia)
🏢 Synthires
📍 Valencia