Simon Willison releases web-edit for browser-based file editing

A new web app for editing files

Simon Willison has released a new open-source project called web-edit 0.1a1. It is a web application that lets users edit text files inside a folder through their browser, without needing to open a command line or a desktop editor.

The tool is still in its first alpha version, meaning it is early-stage software that may have bugs or unfinished features. Release 0.1a1 is the starting point that Willison has shared with the public for testing and feedback.

AI helped make it faster

One notable detail about web-edit is that Claude Opus 5.5, the large language model from Anthropic, was used to write the performance optimizations built into the app. Willison fed the model a Python 3.15 profiling report — a file that shows where the program spends most of its processing time — and Claude Opus 5.5 then wrote the code improvements based on that data ¹.

The profiling report itself was generated by GPT-6 Astra, another large language model, showing a workflow where two AI systems worked together: one gathered the performance data and the other used it to speed things up.

Built on Python 3.15

Willison recently posted about upgrading his projects from older versions of Python to Python 3.15, dropping support for Python 3.10 and using versions 3.11 through 3.15 ¹. Web-edit is written using this newer version of Python, which is a popular programming language used to build websites, tools, and AI applications.

The release also comes alongside a monthly briefing service that Willison offers for a small monthly fee, where subscribers get a curated email summary of the most important developments in large language models.

What comes next

As an early alpha release, web-edit 0.1a1 is aimed at developers and tinkerers who want to experiment with browser-based file editing. Willison has a track record of building practical developer tools and sharing them openly, and he has also been experimenting with new features for his blog built using his voice ¹.

Key facts

• web-edit 0.1a1 is a browser-based file editor in early alpha
• Claude Opus 5.5 wrote the performance optimizations
• GPT-6 Astra generated the profiling report used to guide improvements
• The tool runs on Python 3.15
• Simon Willison announced the release on October 13, 2026

Sources

1. Release: web-edit 0.1a1
2. 2022 in science — en.wikipedia.org