I've made pasta before using 00 flour. I was about to use the same thing to make gnocci but I've noticed that none of the gnocci recipes mention the "00". Does it make a difference? Is one better then the other?
00 is extra-fine flour, the most refined grade. Here's a useful page for more about the old flour grading system. Other than pasta I use it for thickening sauces, and I sometimes make pizza dough with it, although I can't tell the difference between using 00 and good quality bread flour. I'd use 00 for Gnocci certainly as the chefs do, but most home cooks just use plain flour and seem to get good results.
Basically, if you have it or can get it use it, if not plain flour is fine.
Shared from Book: Making Artisan Pasta: How to Make a World of Handmade Noodles, Stuffed Pasta, Dumplings, and More
TYPES OF WHEAT FLOUR Italian Doppio Zero (00) In Italy, flour is milled to various degrees of fineness from 2, the coarsest, to 000, the finest. The number of zeros is unrelated to gluten content. There is 00 flour meant for bread (labeled panifiabile in Italian), for pizza, and for pasta with gluten levels ranging from 5 to 12 percent. In the North, 00 flour produced from soft wheat (grano tenero) and relatively low in protein is preferred for making fresh pasta at home. Some pasta artisans choose slightly grainier 0 flour, and others add some durum flour or semolina for color and strength, as I do in my mix. Look for imported extra-fine Italian doppio zero flour from specialty Italian importers. Molino Caputo, a mill in Naples that specializes in slow-ground artisan flours, produces a special 00 flour labeled “Pasta Fresca and Gnocchi” that is ideal for fresh pasta but not easy to find in the United States.
I would personally recommend using flour with less protein content for gnocchi. <10%
Just a quick aside...I went to make a pie today and discovered I was out of all purpose flour, so I decided to try the 00 I had in the pantry. It's lower gluten content and fine texture made for the best pie dough I've ever made!