Developer Generates Complete Website Using Claude Opus 5 in Single Code-Only HTML File

A developer has demonstrated Claude Opus 5's code-generation prowess by building an entire functional website as a single HTML file, with every visual element—graphics, layouts, interactive components—written entirely in code rather than relying on external images, fonts, or libraries. Released in July 2026, Claude Opus 5 represents a step-change improvement in coding ability over its predecessors, with the largest performance gains in deep reasoning, agentic workflows, and long-horizon programming tasks. The model operates with a 1 million token context window and moderate latency, priced at $5 per million input tokens and $25 per million output tokens—identical to Claude Opus 4.8's pricing but with substantially improved performance.