Is Undertow a Web Server?


Scott Campbell

Undertow is a lightweight, flexible, and high-performance web server written in Java. It provides both embedded and standalone server capabilities, making it a popular choice for building modern web applications. In this article, we will explore the features and benefits of Undertow as a web server.

Why Choose Undertow?

Undertow offers several compelling advantages that make it an attractive option for developers:

  • Lightweight: Undertow has a small footprint and minimal resource requirements. It is designed to be efficient and performant, making it ideal for applications that need to handle a large number of simultaneous connections.
  • Flexible: Undertow provides a modular architecture that allows developers to choose the components they need and customize their server configuration.

    This flexibility enables fine-grained control over the server’s behavior and resource allocation.

  • High Performance: Undertow is known for its excellent performance characteristics. It leverages non-blocking I/O to handle concurrent requests efficiently, resulting in faster response times and improved scalability.

Key Features of Undertow

Let’s dive deeper into some of the key features that make Undertow stand out as a web server:

Embedded Server Capabilities

One of the major strengths of Undertow is its ability to be embedded within other applications. This means you can run your web server directly from your application code, without requiring an external server installation or deployment process.

The embedded mode makes it easy to create self-contained applications with minimal setup and deployment overhead. It also allows for greater control over the server lifecycle, enabling dynamic configuration changes at runtime.

HTTP and WebSocket Support

Undertow provides comprehensive support for both HTTP and WebSocket protocols. It includes a powerful HTTP server implementation with support for HTTP/1.1 and HTTP/2, allowing you to handle web requests efficiently.

In addition, Undertow offers built-in support for WebSocket, a communication protocol that enables real-time bidirectional communication between the server and the client. This feature is particularly useful for applications that require instant updates or live data streams.

Security and TLS Support

Undertow provides robust security features to protect your web applications from common vulnerabilities. It supports various authentication mechanisms, including basic authentication, form-based authentication, and custom authentication providers.

Furthermore, Undertow offers Transport Layer Security (TLS) support out of the box, allowing you to secure your connections with HTTPS. TLS ensures the confidentiality and integrity of data transmitted between the server and client, making it essential for secure web applications.

Getting Started with Undertow

To start using Undertow as your web server, you need to include the necessary dependencies in your project’s build configuration. Undertow is available as a Maven artifact, so you can easily add it as a dependency in your project’s `pom.xml` file:


Once you have added the dependency, you can start configuring and using Undertow within your application code. The official Undertow documentation provides detailed information on how to set up and customize your server for different use cases.


Undertow is a powerful web server that offers lightweight, flexible, and high-performance capabilities. Its embedded mode, support for HTTP and WebSocket protocols, and robust security features make it an excellent choice for developing modern web applications.

By leveraging Undertow’s features, you can build scalable and efficient web servers that meet the demands of today’s dynamic web applications.

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