PlutoPrint supports a large subset of CSS, including flexbox for most common layouts, but it’s not a full browser engine, so there are some limitations. You can see a more complete list of supported features here: https://github.com/plutoprint/plutobook/blob/main/FEATURES.m.... We’re also actively tracking bugs and improvements on the GitHub repo: https://github.com/plutoprint/plutoprint/issues, and contributions or test cases are always appreciated to help expand coverage.