Green onions are sometimes called scallions or spring onions and they're most commonly used in Asian cuisines, but are very popular in other dishes as well. They have a sharp onion flavor, with the white part being more strongly flavored than the green. If you're looking for a substitute, there are several veggies and herbs that can be used in their place, but choose carefully. Some work better in raw dishes, while others are better when cooked, so give that some thought before swapping green onions out. Here's the best sub options:
Leeks have an appearance similar to a fatter green onion, but their flavor is not the same. They do have an intense onion taste, but a rich depth that green onions lack. They're best substituted for green onions in cooked dishes, but are too tough and intensely flavored to work well raw.
Shallots are small, dry onions with a fresh flavor. Use them as a substitute for green onions in cooked dishes, or use very finely minced shallots sparingly in raw dishes. Their flavor can be very pungent when used raw, so use it very lightly, then taste the dish and adjust the amount used to suit your tastes.
Ramps are also known as wild leeks. They grow around the Appalachian Mountains and surrounding states and have an intense onion and garlic hybrid flavor. It's extremely strong, so they should only be used in cooked dishes.
Last, you can substitute fresh chives for green onions in raw dishes. Chives have a very mild onion flavor that's similar to the green section of a green onion. They'll also work in cooked dishes, but their flavor will become almost non-existent, so we recommend sticking with the raw option. Stay away from dried chives unless you have no other option, because their flavor changes dramatically when dried.