Kroki creates diagrams from textual descriptions (2022-12-26)
Kroki is an API and interactive web site which creates diagrams from text.
GraphVis for years...
dot format, and many more formats. Most of them I'd never heard of, so if you like text --> diagram tools, it's worth looking at even for that alone.
Bytefield visualizes binary formats. Several UML formats. and
They also have an interactive demo on the main page.