Updated: Jun 8, 2021
What is the mark of a properly made Neapolitan pizza crust?
The best Neapolitan pizzas should have a thin, thin layer of crispness to the crust, followed by an interior that is moist, light,airy, and cloud-like with good, stretchy chew, and plenty of flavor. The taste of the dough should reflect careful fermentation, which releases flavorful gasses into the air pockets of the crust. You are going to see a varying degree of charring on your pizza. It's almost unavoidable in the heat of a Neapolitan pizza oven. The light charring around the crust of the pizza is known as leopard spotting.
What level of Leopard spotting is acceptable ?
The name is obviously a reference to the little blisters of charred material along the pizza's crust. You are not looking for a browning of the crust, rather you want a leopard-spotted look, with many small dark spots surrounded by paler dough.
Many people, especially pizza-makers, see the leopard spotting or char as desirable. A nice light char will not hurt you and in fact can add a new layer of flavor and texture to the pizza. But if these dark spots are bitter and/or acrid, that could be burned !
Charring gives the pizza a smoky flavor, the absence of charring indicates that the oven may not be at the high temperatures needed to produce a "proper" Neapolitan pizza
How to tell if its Leopard spotting, Burnt or Cold dough used in the oven?
Below is a good example of what you are looking for in the crust of your Neapolitan Pizza image is provided by @peddling pizza, you can see an overall even coverage of the darker spots and a few of the larger dark spots.
Below image is what you want to avoid. This is caused by the use of cold dough being used in the pizza oven. The pizza dough needs to be brought up to room temperature before it is used.
The perfect level of blistering is achieved by having a dough with a very well developed gluten structure, combined with gentle handling for the crust when stretching the dough to keep as much air trapped in the crust as possible. But most importantly the application of high heat to create the release of steam and a good rise in the dough. The proper leoparding in a neapolitan pizza should be small, micro blisters around the crust, possibly with occasional large bubbles.