Tools
A collection of small, privacy-friendly utilities that run in your browser. Nothing is sent to a server unless a tool says so on its page, such as fetching games by username or sharing a room.
Networking
Client Info
See the public network and browser details visible to websites: your IP address, ASN, network provider, approximate location, time zone, browser, device, screen, and connection information.
ASN Conversion
Convert BGP autonomous system numbers between asplain, asdot, and asdot+ notation. Shows the hexadecimal value, whether the number fits in the 2-byte range, and flags private, documentation, and reserved ranges from the relevant RFCs.
Subnet Calculator
IPv4 and IPv6 subnet calculator in one input. Auto-detects the address family, accepts a prefix length or dotted mask, counts inclusive IPv4 and IPv6 ranges, applies classful defaults, lists resulting subnets, and maps IPv4 networks to their IPv4-mapped, 6to4, and NAT64 transition forms.
Network Toolkit
Five utilities in one page. A CIDR summarizer that aggregates prefix lists, a VLSM planner that allocates subnets largest first, an ACL wildcard helper including non-contiguous wildcards, a MAC address tool with EUI-64 and SLAAC derivation, and a tester for BGP AS-path regular expressions and prefix-lists.
Classroom
Randomizer
Import an Excel roster or paste a table, then pick names fairly without repeats. A private Mafia mode assigns one secret role per player, while session history stays tucked inside a slide-over drawer.
Math and Writing
Function Graphs
Plot mathematical functions interactively. Supports standard math notation with zoom and pan controls.
Math Formula
Type LaTeX, see it rendered live, then copy as a high-resolution PNG image, SVG, or in multiple formats (MathML for Office, Python/SymPy, Unicode for plain text). Includes a handwriting recognition pad for drawing formulas.
LaTeX Preview
Full-featured LaTeX editor with live preview, symbol palette, document templates, command autocomplete, and export to PNG/SVG/PDF/HTML/Markdown. Supports sections, theorems, lists, math environments, and inline formatting.
Markdown Preview
Markdown editor and viewer with live preview. Reads Markdown and GitHub flavored Markdown, Quarto and R Markdown, HTML, JSON, and CSV or TSV data. Renders math, Mermaid diagrams, syntax highlighted code, tables, task lists, footnotes, and callouts. Drop a file onto the page to open it, then export to HTML, PDF, PNG, or plain text.
Astronomy
Eclipse Atlas
Pick any solar or lunar eclipse and watch it unfold on a zoomable world map or globe. For solar eclipses it draws the penumbra sweeping across the Earth, the small umbra whose track is the path of totality, and the center line where totality lasts longest. For lunar eclipses it shows the hemisphere that can see the event, plus a cross-section of Earth’s shadow with the Moon’s track through it. Drop a pin anywhere for contact times, the altitude of the Sun or Moon, and how much of the disc is covered, in Universal Time or in the local clock at that spot. Country and city names fill in as you zoom, with an optional street-level basemap for planning where to stand. Charts are monochrome in the style of a printed star atlas, with night and red palettes for use in the dark.
Planetarium
A solar system orrery and a full sky map in one instrument, sharing a single time machine that spans the years -3000 to 5000. The orrery looks down on the planets running their true-scale orbits, with the Moon appearing on its real orbit once you zoom in on Earth. The sky views draw nearly three thousand naked-eye stars with their proper motions, the modern constellation figures, the colored planets and Moon, the Milky Way band, and the famous deep sky objects from the Orion Nebula to Andromeda, either as an all-sky dome or as a horizon view seen by a little observer you drag around a globe. A slider sweeps any span from a single day to a whole millennium, so one press of Play shows the sky rotating, the Moon cycling, Mars looping in retrograde, or precession handing the pole star from Thuban to Polaris and onward.
Design
Diagrams
A full diagram editor for flowcharts, network and cloud architecture drawings, UML, entity relationship diagrams, org charts, mind maps, and BPMN. It opens in the browser and runs entirely on your own machine, with no account and no upload: saving writes the file straight to your downloads folder. A macOS build of the same editor is available for working offline. Built as an independent fork of draw.io under the Apache License 2.0, with the telemetry and third party conversion endpoints of the original removed.
SVG Preview
Paste or upload SVG code and see it rendered instantly. Useful for previewing diagrams and icons.
Color Pallet
Pick a number of colors and an optional starting color, and get a theme palette built from color wheel harmonies computed in the perceptual OKLCH space (or the classic HSL wheel). Each swatch shows its hex value, color coordinates, and WCAG contrast rating, with click to copy and a ready CSS variables block.
Typography
Choose a typeface for scientific writing and see how it behaves. Audition around forty text, sans, and monospaced faces, each tagged with its math companion and LaTeX package, then preview the result as a web article or as a printed page at real trim size, including approximations of the IEEE Xplore, MDPI, and ScienceDirect layouts. Live metrics report x-height, characters per line, lines per page, and which Greek and math glyphs the face is missing. One button restyles the page you are on, another carries the choice to the whole site and remembers it in your browser, and the settings export as a CSS variables block and a LaTeX preamble.
T-shirt Design
Start with one of eight garment fits—including dedicated women’s and kids’ cuts—and its shirt color, then build a finished quote composition in a single-screen studio. A collapsible seven-step workflow surrounds the live mockup with ten text-aware placements, curated typography, adjustable logo layering, ink palettes, and spacing controls. Export an editable, transparent 12 × 15 inch print SVG or a presentation mockup; everything runs locally in the browser.
Chess
Chess Coach
Play timed games (15+10 and more) against twenty characters from absolute beginner (200) all the way to raw Stockfish (3600+), each with their own personality, strengths, and weaknesses. A built-in coach hints at the right piece if you think too long, warns you in orange/red before you commit a mistake or blunder, estimates your rating as you play, and hands you a post-game grandmaster review. Tracks your progress and game history in your browser, with an optional online leaderboard. Powered by Stockfish, Maia, and Leela Chess Zero neural networks, all running in your browser.
Game Review
Drop the PGN files of your games, or fetch them by username, and the engine reviews every move in your browser. The page names the weaknesses that cost you the most points, with the moments as evidence, lists your strengths, and builds a set of positions to practice, from your own games and from the Lichess puzzle database, each played for several moves and graded. Run it again on the next batch of games to see the trend.
Reassess Your Chess
A self paced course through Jeremy Silman’s imbalances, in eleven parts: the imbalances themselves and how to plan with them, knights, bishops, the minor piece war, rooks, chess psychology, target consciousness, statics against dynamics, space, passed pawns, and the opening, with rating banded tests along the way. Each lesson gives you a position, a short read, and exercises you answer on the board itself, asking which piece to move, which piece must stay, where a piece belongs, or what the position is really about. Finish a lesson and it turns green, which unlocks the next one. Positions follow Jeremy Silman, How to Reassess Your Chess, fourth edition.
Daily Chess Puzzles
Solve a fresh set of curated Lichess puzzles every day, from a plan that spans two years and ramps up in difficulty. Completed days stay on the calendar, and you can click one to review its puzzles.
Chess Tournament
Run a Swiss-system tournament for a club or a company. Import the players from a spreadsheet with their company and FIDE ratings, split them into sections, pair each round, enter the results, and get standings with FIDE-style tiebreaks and a rating for every player. Save it to your account or as a file.