Simon Willison's blog offers a mix of technical tutorials, data analysis projects, and reflections on technology and society. With a focus on Python, SQL, and web development, Simon shares insights into building web applications, working with data, and exploring emerging technologies. Developers can learn about data visualization, API design, and software engineering best practices, gaining inspiration and practical knowledge to advance their careers.

Simon Willison

GPT-5.5 has launched, available in OpenAI Codex and rolling out to paid ChatGPT subscribers, but without API access yet. Simon Willison discovered that OpenAI officially supports using the Codex subscription endpoint (used by Codex CLI, OpenCode, and Pi) for third-party integrations. He used Claude Code to reverse-engineer the openai/codex repo and built llm-openai-via-codex, a plugin for his LLM tool that lets users run prompts against GPT-5.5 using an existing Codex subscription. The post also demonstrates the model's SVG generation capability via his 'pelican riding a bicycle' benchmark, comparing default vs. high-reasoning outputs.

A pelican for GPT-5.5 via the semi-official Codex backdoor API