Fresh herbs blacken or wilt in the oven

Cosmetic

Almost always fresh herbs added before baking instead of as a post-bake finishing touch.

Ask yourself

#1
Fresh, delicate herbs added before baking rather than after
Strongly supported
Thin fresh leaves like basil have very little moisture and mass to protect them; oven heat, especially at high Neapolitan-style temperatures, dries and chars them well before the pizza itself is done.
#2
Herbs placed directly on top rather than tucked under cheese or sauce for partial protection
Generally accepted
Fully exposed leaves have no protection from direct radiant heat, unlike herbs partially shielded under cheese.

The same symptom has different answers on different equipment. Each branch below states how to tell whether it is yours.

Pizza in a domestic ovenStrongly supported
How you would know: Basil leaves placed on top before baking came out black and brittle after a bake of several minutes.
A domestic-oven bake is many times longer than the bake the Neapolitan convention of baking basil on assumes. Thin leaves exposed on top dehydrate within a minute or two and then char.
Do now: Remove the blackened leaves and add fresh ones now — residual heat will release their aroma.
Change next time: Add basil after the bake, or tuck it under the cheese where it steams rather than burning. The bake-it-on convention does not transfer from a 90-second oven to a 10-minute one.

Pick off visibly blackened leaves; the pizza is otherwise unaffected

Add delicate fresh herbs after baking rather than before, as a finishing touch, reserving any pre-bake herbs for sturdier, less delicate ones

Guides that treat this as an outcome to improve, an environment to work with, or a flavour to understand, rather than only a problem to fix.