FAQ - GEDv
What version(s) / flavor(s) of the GEDCOM standard does webtrees use and support?
webtrees aims to follow the GEDCOM v5.5.1 standard, while also supporting some of the more common extensions created by other applications.
The software can read pretty much any dialect/version of GEDCOM and edit/display it. If there is a GEDCOM structure (from either 5.5.x or 7.0.x) which is not displaying correctly, that is probably a bug.
More information at gedcom