Undertow vs Wildfly: What are the differences?
Undertow: A flexible performant web server written in java. It is a flexible performant web server written in java, providing both blocking and non-blocking API’s based on NIO. It has a composition based architecture that allows you to build a web server by combining small single purpose handlers. The gives you the flexibility to choose between a full Java EE servlet 4.0 container, or a low level non-blocking handler, to anything in between; Wildfly: A Java EE8 Application Server. It is a flexible, lightweight, managed application runtime that helps you build amazing applications. It supports the latest standards for web development.
Undertow and Wildfly can be categorized as "Web Servers" tools.
Sweazer, Liferay, and STYLIGHT are some of the popular companies that use Wildfly, whereas Undertow is used by CurrencyFair, Notify-e, and Kreomi. Wildfly has a broader approval, being mentioned in 21 company stacks & 22 developers stacks; compared to Undertow, which is listed in 8 company stacks and 5 developer stacks.