I am probably misunderstanding your requirements but if you are looking for something like regex101 then https://omrelli.ug/nearley-playground/ https://omrelli.

I am probably misunderstanding your requirements but if you are looking for something like regex101 then https://omrelli.ug/nearley-playground/ https://omrelli.ug/nearley-playground/ and https://bnfparser.firebaseapp.com/ https://bnfparser.firebaseapp.com/ although not sure how much 'practical' are they. Googling gives [2], [3], [4]. [2] https://mingodad.github.io/parsertl-playground/playground/ https://mingodad.github.io/parsertl-playground/playground/ not sure. [3] https://chrishixon.github.io/chpeg/playground/ https://chrishixon.github.io/chpeg/playground/ [4] https://mdkrajnak.github.io/ebnftest/ https://mdkrajnak.github.io/ebnftest/