ASCIIFlow
asciiflow.com
Draws boxes and arrows as plain ASCII you can paste into a comment
No sign-upOn device
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asciiflow.com
Draws boxes and arrows as plain ASCII you can paste into a comment
coggle.it
Mind maps that stay readable as branches multiply
diagrams.net
Full diagram editor that works without an account or a saved file
excalidraw.com
Hand-drawn-looking whiteboard that opens instantly with no sign-up
lucidchart.com
Polished diagramming with real-time collaboration and smart layout
markmap.js.org
Turns a Markdown outline into a collapsible mind map as you type
mermaid.live
Write a diagram as text and watch it render beside you
mural.co
A shared canvas of sticky notes for running a workshop remotely
plantuml.com
Renders UML from a text description, with the source encoded in the URL
sequencediagram.org
Purpose-built editor for sequence diagrams, typed rather than dragged
tldraw.com
Infinite canvas that feels like a native app in a browser tab
whimsical.com
Flowcharts, wireframes, mind maps and docs on one fast canvas
wireframe.cc
Draw a rectangle and it guesses which UI element you meant
Where these come from
A real job usually crosses two or three categories, which is why starting from the task is often faster than starting from the shelf.
Questions
For anything you will edit again, prefer a tool that saves to a file you own or to a text format you can version. Text-to-diagram tools are slower for the first draft and dramatically faster for the fifth.
Yes — 9 of the 13 sites listed here work with no account at all. They are marked "No sign-up" and you can spot them by the green rule down the left edge of the card.
7 of these do the work inside your browser and never upload the file — those are the ones to use for anything with personal data in it. The rest send your input to their servers, which is fine for public material.