VisualVM

VisualVM is an open-source visual tool for monitoring, troubleshooting, and profiling Java applications. It provides a unified interface to view local and remote Java Virtual Machines (JVMs) and combines several command-line JDK tools into a single product. VisualVM is built on the NetBeans Platform and is distributed with some Java Development Kit releases as well as available as a standalone download from the VisualVM project.

Key features include real-time monitoring of CPU and memory usage, garbage collection activity, and thread activity. It can attach to running JVMs to collect data, take heap dumps, and analyze memory consumption for leak detection. VisualVM supports CPU and memory profiling, offering both sampling and instrumentation modes. Sampling incurs lower overhead, while instrumentation provides detailed method-level data. The tool can display memory histograms, live graphs, and heap dump analysis to help identify performance bottlenecks and inefficient code paths.

VisualVM supports remote monitoring and profiling through various mechanisms, including Java Management Extensions (JMX) and the Attach API, enabling analysts to connect to remote JVMs with appropriate permissions. Its functionality is extended by plugins, enabling additional analyzers, visualizations, and compatibility with specific frameworks or application servers. VisualVM is cross-platform, running on Windows, macOS, and Linux.

Originating from Sun Microsystems and now maintained by Oracle and the community, VisualVM integrates with the broader Java tooling ecosystem. It is commonly used by developers and operators to diagnose performance issues, optimize memory usage, and gain insight into application behavior during development and in production environments.