Drawpile vs PD Howler

Drawpile is a drawing, painting, sketching and animation app for people working together on one canvas, with offline use also available. It runs on Windows, macOS, Linux, Android and the web; on iPhone and iPad, the browser version works, but there is no native iOS app. Its toolkit includes more than 200 built-in brushes, several brush engines, a brush editor and stroke stabilization. Layers and layer groups support blend modes, alpha preserve, clipping groups, masking and alpha lock. Animation tools include a timeline and onion skins. Canvases can be saved as OpenRaster or PSD, and images can be pasted from files or other programs. Users can join official community servers without arranging their own infrastructure, or operate a server themselves. External authentication can let users access potentially untrusted third-party servers without sharing their password with those servers. Drawpile says it does not transfer information to other networked systems unless a user or operator specifically requests it. The free plan costs nothing.

PD Howler has no write-up on Specifiction yet; its figures are above.