It doesn't allow specifying which OpenType features to keep and which not, though. Tabular numbers are useful, and I've also found some use for small caps for e

It doesn't allow specifying which OpenType features to keep and which not, though. Tabular numbers are useful, and I've also found some use for small caps for example. FontSquirrel also has a similar generator and converter which in theory gives more detailed control over which features to keep, although in practice an attempt to subset Fira Sans or FiraGO produced a font with broken ligatures, so not all that useful for me, either. In the end I've ended up just subsetting and converting the font myself using the Python FontTools.