Thymeleaf is a Java library that is open-source and licensed under the Apache License 2.0. It's a template engine that supports HTML5, XHTML, and XML. It is a server-side Java template engine that may be used in both web (servlet-based) and offline (non-web) settings. It's ideal for HTML5 JVM web development today. It has a complete Spring Framework integration.
To show data or text generated by the program, it applies a set of transformations to template files. It can be used in web applications to serve XHTML/HTML5.
Thymeleaf's purpose is to make building templates more elegant and well-formed. It is built on the foundation of XML tags and attributes. Instead of directly defining that logic as code inside the template, these XML tags describe the execution of predefined logic on the DOM (Document Object Model). It's a JSP replacement.
Thymeleaf's architecture provides for quick template processing thanks to the caching of parsed files. During execution, it does as little I/O operations as feasible.