Jinja2 custom template tags are, to quote their website "non-trivial" to implement, and so poorly documented that you are stuck trying to figure out how the tag

Jinja2 custom template tags are, to quote their website "non-trivial" to implement, and so poorly documented that you are stuck trying to figure out how the tags work from source. Poorly documented? http://jinja.pocoo.org/2/documentation/extensions#module-jinja2.ext http://jinja.pocoo.org/2/documentation/extensions#module-jin... I agree that the parser API is not exactly pretty - but creating your own tag starting from that example is pretty straightforward. I have created many tags myself (mostly the standard case of mutating the enclosed content in one way or another) and can't complain. It took me literally minutes to get my first tag working - perhaps you are referring to an older version of jinja?