Simon Willison’s Weblog

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Tool DOT File Renderer — Render DOT graph files into visual diagrams directly in your browser. Paste your DOT syntax into the textarea and the graph will automatically render as an SVG visualization, with live updates as you edit. Share your graphs by copying the URL, which encodes your DOT content in the fragment identifier.
10th Oct 2025, 11:16 pm
Tool JSON String Extractor — Extract all strings from JSON data that exceed 20 characters in length or contain line breaks. This tool is useful for identifying longer text content within complex JSON structures for review, localization, or documentation purposes. Simply paste JSON into the textarea to automatically display matching strings along with their object paths, and use the copy button to quickly transfer any string to your clipboard.
5th Oct 2025, 11:14 pm
Tool Keyboard Debugger — Monitor keyboard input in real-time with this interactive keyboard debugger that displays pressed keys and their corresponding key codes. Press any keys on your keyboard to see them appear with visual feedback, including support for simultaneous multi-key presses and special key representations. This tool is useful for testing keyboard functionality, debugging input handling, and understanding key event properties like key name, code, and keyCode values.
28th Sep 2025, 9:55 pm
Tool MicroPython Code Executor — Execute Python code in a sandboxed MicroPython WebAssembly environment with output displayed in real-time. Code is automatically saved to the URL for convenient sharing and persistence, and the environment supports JavaScript interoperability including the `fetch()` API for making HTTP requests. Built-in examples demonstrate common programming patterns from basic operations to working with APIs.
25th Sep 2025, 3:44 pm
Tool NumPy Vectors & Matrices — Pyodide Lab — Execute NumPy vector and matrix operations directly in your browser using an interactive lab powered by Pyodide. Work through five hands-on exercises covering elementwise operations, dot products, matrix multiplication, broadcasting, and indexing, then experiment freely in the playground sandbox with instant Python output.
24th Sep 2025, 11:35 pm
Tool Badge Drawer — Device-Scale Canvas — # Badge Drawer — Device-Scale Canvas
16th Sep 2025, 4:15 pm
Tool GitHub Account Info Lookup — Look up GitHub user account information by entering a username to retrieve the numeric Account ID and account creation date through the public GitHub API. The tool displays the user's profile link, avatar, and formatted timestamps, along with request latency information. Unauthenticated requests are subject to GitHub's rate limits, which may block further lookups after a certain number of queries.
11th Sep 2025, 7:09 pm
Tool AI Adoption Rolling Avg — Pyodide — View AI adoption trends across different firm sizes by analyzing survey data on artificial intelligence usage in the workplace. This page runs a Python analysis using Pyodide to fetch employment survey data, calculate six-survey rolling averages, and generate an interactive visualization showing adoption rates by company size from November 2023 through August 2025. Download the resulting chart as PNG or SVG for further use or presentation.
8th Sep 2025, 8:14 pm
Tool Pyodide Bar Chart Demo (pandas + matplotlib) — Execute Python code directly in your browser with Pyodide, a WebAssembly-based Python runtime. This demo loads pandas, numpy, and matplotlib in the client to generate a bar chart from sample data and display it as a rendered image—no server required. The first run may take a few seconds as the necessary libraries are downloaded from CDN, but subsequent executions run instantly from your browser's cache.
8th Sep 2025, 7:17 pm
Tool Devon Lane Driving Simulator — Navigate the treacherous single-track lanes of rural Devon in this interactive driving simulator, where you must manage your sanity while encountering cyclists, tractors, caravans, and other obstacles. Each encounter presents a unique challenge requiring a dice roll to succeed, with your choices affecting both your progress and mental state as you attempt to travel increasingly longer distances.
4th Sep 2025, 12:39 pm
Tool Rich Text to Markdown — Convert rich text from your clipboard into properly formatted Markdown by pasting content into the input area. The tool automatically detects formatting such as bold text and converts it to Markdown syntax while removing unnecessary leading spaces from each line. Supports rich text format (RTF) from terminal output, HTML from web pages, and plain text input.
22nd Aug 2025, 11:07 pm
Tool Hacker News comments for a user — View Hacker News comments for any user by entering their handle and fetching up to 1,000 recent comments in a single request. The tool displays each comment with its date, story title, direct links to both the comment and discussion thread, and the full comment text, which can be easily copied to your clipboard. This makes it convenient to archive, analyze, or review a user's comment history on Hacker News.
19th Aug 2025, 7:38 pm
Tool Percentage Recalculator — Calculate and rescale percentage values in real time with this interactive tool. Enter up to four percentages and optionally mark any as ignored to exclude them from the recalculation, which automatically normalizes the remaining active percentages to sum to 100%. The interface displays both the original values and their recalculated equivalents, making it useful for adjusting weighted distributions or normalizing survey responses.
8th Aug 2025, 3:05 pm
Tool Alt Text Extractor — Extract images and their associated metadata from pasted web content with this tool. When you paste rich text containing images, the application automatically retrieves each image's alt text, URL, and generates ready-to-use Markdown and HTML code snippets. Each extracted element can be individually copied to your clipboard for use in documentation, accessibility audits, or content management.
25th Jul 2025, 10:58 pm
Tool Bullish vs Bearish - Remember Which is Which! — Learn the difference between bullish and bearish market sentiment through an interactive visual guide featuring animated bull and bear characters. The page uses intuitive animal metaphors—bulls thrust their horns upward to represent rising markets and optimism, while bears swipe downward to represent falling markets and pessimism. A built-in quiz feature helps reinforce these concepts with randomized questions about market terminology.
21st Jul 2025, 2:12 pm
Tool Speech Synthesis Tester — Test the Web Speech API's speech synthesis capabilities by entering text and configuring voice parameters such as rate, pitch, and volume. The application provides a selection of available system voices and displays real-time status updates as text is being spoken. Users can adjust synthesis settings and stop playback at any time using the intuitive control interface.
20th Jul 2025, 4 pm
Tool Open Sauce 2025 Schedule — Browse the Open Sauce 2025 conference schedule with sessions organized by day, including speaker information, session duration, location, and detailed descriptions. Users can search for specific sessions across all three conference days (July 18-20, 2025) and download the entire schedule as an ICS calendar file for integration with their calendar applications. The interface displays current and upcoming sessions in Pacific Time to help attendees plan their conference experience.
17th Jul 2025, 5:33 pm
Tool Hacker News, filtered — Browse the latest Hacker News stories with customizable content filtering to exclude topics of your choice. Enter comma-separated terms to filter out posts matching those keywords across titles, URLs, and descriptions, and refresh the feed to load the newest stories. Your filter preferences are automatically saved in your browser for future visits.
15th Jul 2025, 3:10 pm
Tool FFmpeg video crop — Generate FFmpeg crop commands by uploading a video file and interactively defining a crop area using a draggable overlay. The tool provides both standard and iPhone-compatible FFmpeg command formats that automatically update as you adjust the crop box dimensions and position. This eliminates the need to manually calculate crop parameters for video editing workflows.
9th Jul 2025, 6:09 pm
Tool Hacker News Multi-Term Histogram — Analyze Hacker News stories by searching for multiple terms across a custom time range and visualize the results as an interactive histogram. The tool fetches monthly hit counts from the Hacker News API for each search term, displaying data in a color-coded bar chart, sortable table, and exportable JSON format. Click any bar to view the actual stories matching that term within that month's date range.
7th Jul 2025, 12:02 am
Tool JSON to Markdown Converter — Convert JSON transcripts from audio into formatted Markdown with speaker names and timestamps. This tool automatically processes JSON data containing speaker names, text, and timestamp information, formatting them into readable Markdown output that can be easily copied and pasted elsewhere. The tool includes instructions for generating the required JSON format using the LLM command-line tool with audio files.
17th Jun 2025, 6:53 pm
Tool Reading Time Estimator — Calculate reading time estimates for any text by pasting or typing content into the input area. The tool displays real-time statistics including word count, character count, and estimated reading duration based on an average reading speed of 230 words per minute. The reading time adjusts dynamically, showing minutes for shorter texts and hours plus minutes for longer content.
17th Jun 2025, 3:41 pm
Tool Multi-Tab Sync Chat — Send chat messages that synchronize instantly across multiple browser tabs using the Broadcast Channel API. Each tab displays messages sent from other tabs with a sync indicator, allowing real-time communication without requiring a backend server. Open multiple tabs of this page to see messages propagate automatically across all instances.
8th Jun 2025, 3:46 pm
Tool Transfer time calculator — Calculate file transfer duration by entering the file size and transfer speed with their respective units. The calculator automatically converts between different measurement units (GB, MB, TB for file size; Mbps, MB/s, KB/s for speed) and displays the estimated transfer time in an easily readable format. Results include a detailed breakdown showing days, hours, minutes, and seconds alongside the calculation parameters.
7th Jun 2025, 8:31 pm
Tool Date Calculator — Calculate the time between two dates with detailed breakdowns and visual representations. This tool displays the total number of days, weeks, business days, and weekend days spanning your selected date range, along with a visual timeline showing where the dates fall relative to today. Use the calculation method options to focus on specific day types such as business days or weekends only.
4th Jun 2025, 3:16 am
Tool Interactive CSS Flexbox Playground — Experiment with CSS Flexbox properties in real-time using this interactive playground. Adjust container properties like flex-direction, justify-content, and align-items while watching the layout change instantly, then select individual items to customize their flex-grow, flex-shrink, flex-basis, and alignment settings. The dynamically generated CSS code output shows the exact syntax needed to recreate your layout, making it an effective learning tool for mastering flexbox concepts.
24th May 2025, 4:47 pm
Tool Conference Schedule - ICS File — Download and view the complete conference schedule for May 22, 2025, in iCalendar format. This page provides access to all 25 events from the San Francisco conference, including keynotes, technical sessions, workshops, and office hours, which can be imported directly into your calendar application. A live preview of the ICS file contents is displayed below the download button for reference.
22nd May 2025, 2:26 pm
Tool Annotated Presentation Creator — Create annotated presentation slides with alt text and markdown notes. Upload your slide images, add accessibility descriptions and annotations with markdown support, then generate HTML output using customizable templates. The tool automatically saves your work and includes optional OCR functionality to extract text from slides.
15th May 2025, 2:13 am
Tool Render JSON from Gemini Image Generation — Parse and visualize JSON responses from the Google Gemini image generation API, extracting and displaying generated images, text content, and usage metadata in a formatted layout. The tool supports direct JSON input through paste or by loading example datasets, making it useful for testing and inspecting Gemini API outputs including model version information and token usage statistics.
7th May 2025, 9:56 pm
Tool HTML Live Preview — Write HTML code directly in the editor pane and see the rendered output update in real-time in the preview pane. The editor supports live preview with debounced updates to prevent excessive rendering, and includes a copy button to save your HTML code to the clipboard. On mobile devices, toggle between the editor and preview views using the dedicated button in the toolbar.
30th Apr 2025, 2:55 am

Years