Simon Willison's Weblog: Tools

markdown-svg-renderer

2026-05-28T19:45:14+00:00

View Mozilla Bugzilla bug reports and render formatted markdown content with live preview. Paste markdown directly or load from a raw URL or GitHub Gist, with support for standard markdown formatting, tables, code blocks, and interactive SVG previews with tabbed display. Toggle between editor and full-screen viewer modes to focus on the rendered output.

Mad House — Usborne Creepy Computer Games

2026-05-24T17:14:11+00:00

Mad House — Usborne Creepy Computer Games

Play a retro text-based escape game inspired by 1980s Usborne computer books, where you control doorways in a shifting house to align three exits before footsteps catch you. Use keyboard controls (X/C and N/M) or on-screen buttons to move the near and far doorways left and right, while the center doorway moves unpredictably. The game features authentic CRT phosphor aesthetics with scanlines and a pulsing HUD that tracks your remaining time and door alignment status.

Curly Quote and Em Dash Highlighter

2026-05-21T20:51:47+00:00

Curly Quote and Em Dash Highlighter

Identify curly quotes, curly apostrophes, and em dashes in your text with this highlighting tool. Paste or type content into the input panel to see matching characters highlighted in the preview, with real-time counts for each character type. This utility helps detect typographic characters that may have been introduced through word processors or web copy.

QR code generator

2026-05-15T04:00:49+00:00

QR code generator

Generate scannable QR codes from URLs, text, or WiFi network details with customizable styling options. The tool supports multiple encoding modes, including WiFi networks with security settings, and offers various visual styles such as square or liquid designs with adjustable sizes and colors. Generated codes can be downloaded as PNG images or copied directly to the clipboard.

CSP Allow-list Experiment

2026-05-13T04:50:45+00:00

CSP Allow-list Experiment

Experiment with Content Security Policy (CSP) allow-lists by editing HTML code in the left panel and observing how network requests are handled in the sandboxed preview on the right. Add trusted origins to the connect-src allow-list, and the application will prompt you to approve blocked requests from the sandbox, automatically updating your CSP configuration. This tool helps developers understand how CSP policies control resource loading and test dynamic allow-list management in real-time.

Big Words

2026-05-07T18:47:09+00:00

Big Words

Display and customize large text with real-time formatting options including fonts, colors, gradients, and effects. Double-click or double-tap the display area to open the settings panel and adjust text content, styling, and background appearance. Share your creations by saving the customized URL with all your settings encoded as query parameters.

GitHub Repo Stats

2026-05-07T07:25:14+00:00

GitHub Repo Stats

View GitHub repository statistics including commit counts, contributor information, language breakdowns, and release details by entering a repository name or URL. This tool fetches data directly from the GitHub REST API in your browser, displaying comprehensive metrics such as stars, forks, branches, tags, and activity timestamps. Optionally authenticate with GitHub to increase your API rate limit from 60 to 5,000 requests per hour.

Redis Array Playground

2026-05-04T15:53:57+00:00

Redis Array Playground

# Redis Array Playground

iNaturalist Sightings

2026-05-01T19:35:41+00:00

iNaturalist Sightings

# Documentation

Millisecond Converter

2026-04-24T04:23:11+00:00

Millisecond Converter

Convert milliseconds into multiple time units with this interactive tool that displays the duration in seconds, minutes, hours, days, weeks, and a human-readable format. The converter accepts numbers with commas or underscores for readability and provides both a compact breakdown (e.g., "3 minutes, 7 seconds, 238 milliseconds") and a clock-format representation. Results can be copied to the clipboard with a single click for easy sharing or documentation.

datasette.io news preview

2026-04-16T00:18:03+00:00

datasette.io news preview

Preview and validate datasette.io news entries in YAML format with real-time rendering and markdown linting. The editor loads the current news.yaml file from GitHub and provides immediate feedback on formatting errors, link validation, and markdown syntax issues while displaying a styled preview of how entries will appear on the live site. Use the error badge to track validation issues and fix them directly in the editor pane.

Gemini 3.1 Flash TTS

2026-04-15T16:41:46+00:00

Gemini 3.1 Flash TTS

Convert text to natural-sounding speech using Google's Gemini 3.1 Flash TTS model with support for both single-speaker and multi-speaker conversation modes. The tool allows you to customize voice selection, apply directorial tags like `[whisper]` and `[short pause]` for dynamic delivery, and download the generated audio as a WAV file. Requires a valid Gemini API key to function.

SQLite Query Result Formatter Demo

2026-04-11T19:35:31+00:00

SQLite Query Result Formatter Demo

Format SQLite query results in 20 different styles including box-drawing tables, CSV, JSON, HTML, Markdown, and more using this interactive WebAssembly-based demonstration. Adjust formatting options like column headers, screen width, NULL display values, and border styles in real-time to see how your SQL queries render across all available output modes. The demo database includes sample tables for employees, products, and orders with pre-built example queries showcasing each formatting style.

GitHub Repo Size

2026-04-09T21:31:50+00:00

GitHub Repo Size

Check the size of any GitHub repository by entering the owner and repository name or pasting a GitHub URL. The tool fetches repository data from the GitHub API and displays the total size in kilobytes, megabytes, or gigabytes depending on the repository's scale. Results are automatically saved to the browser URL, allowing you to share or revisit repository size checks.

Cleanup Claude Code Paste

2026-04-06T02:55:23+00:00

Cleanup Claude Code Paste

Clean up Claude Code terminal output by removing the ❯ prompt character, fixing whitespace from line wrapping, and joining broken lines into readable paragraphs. Paste your terminal text into the input field and the cleaned output will appear automatically, ready to copy to your clipboard.