A workaround is turning off subpixel antialising. I found similar artifacts in the font rendering in this issue. https://github.com/electron/libchromiumcontent/issues/384 The libchromiumcontent issue links to this one, which describes why this happens: https://bugs.chromium.org/p/skia/issues/detail?id=6663 With a recent change, FreeType no longer adds LCD padding by default, but only when this is necessary. This changes the bitmap offset and size. Maybe a solution could be to update the bundled version of Chromium/NW.js?