Strike

Strike is a web-based, 1-bit paint tool, primarily for quick sketching or line-drawing.

Standalone link to the tool

Source on Github

Features

• brush / eraser / fill tools with different brush shapes and sizes
• 16-‘color’ palette via dither patterns. Each pattern is treated as a separate color for fill tool
• ~50 step undo / redo (it’s fragile, so don’t rely on it too much)
• import PNG and JPG files, which will be converted to 1 bit form
• zoom via mouse scroll or two-finger pinch
• basic image transform tools (flip / mirror / resize canvas)
• save images as a 16-color greyscale (which will import back into Strike with all patterns intact), or as 1-bit black and white image
• autosave (see notes)

Strike is supported on mobile devices and tablets; I personally use it with an iPad Pro.