This internship report presents an analysis of the performance of the Proxsis Group website (proxsisgroup.com) based on Core Web Vitals using the Lighthouse Audit method. The internship was carried out at PT Malaka Incorpora Teknologi (a Member of Proxsis Group) during the February-June 2026 period. The research aims to analyze the condition of Core Web Vitals, identify the technical factors causing performance issues, evaluate compliance with Google's standards, and formulate improvement recommendations. Testing was conducted using Google Lighthouse version 13.0.2 in both Desktop and Mobile configurations, along with Google PageSpeed Insights (PSI) for field data from real users. The test results show that the Performance score falls into the Needs Improvement category (52-61) across all scenarios. The Largest Contentful Paint (LCP) metric emerged as the most critical issue, recording 8.5 seconds on Lighthouse Desktop and 29.7 seconds on Lighthouse Mobile. Based on PSI field data, the website was declared Failed in the Core Web Vitals Assessment on the mobile platform due to a field LCP value of 3.1 seconds, which exceeds Google's threshold. In contrast, Cumulative Layout Shift (CLS) showed consistently good performance across all test scenarios. Three main technical factors behind the issues were identified: unoptimized images (1,771 KiB), the presence of render-blocking resources (estimated impact of 3,550 ms), and slow server response time (TTFB of 1.9 seconds). Improvement recommendations are prioritized on optimizing hero section images through conversion to WebP/AVIF format and preload implementation, eliminating render-blocking resources, and improving server response speed.