Memory

JVM Memory & Garbage Collection Tools

OutOfMemoryError reports, growing heap graphs in your monitoring, and slowly-rotting response times are usually signs one of two things: a leak, or excessive garbage-collection pressure. The tools in this category are how you turn those symptoms into an exact cause.

Two distinct workflows matter here. Heap-dump analysis answers 'what is holding onto this memory' (Eclipse MAT, jmap -dump). GC log / GC behavior analysis answers 'why is the collector working so hard' (GCViewer, gceasy, -Xlog:gc). Most teams need both.

What you'll find here: Capture a heap dump: jmap -dump:live, /diagnostic/jmap/status · Find leaks & dominators with Eclipse MAT · Analyze GC logs with GCViewer or gceasy · Understand modern collectors: G1, ZGC, Shenandoah, Parallel

Memory tools

Eclipse MAT
The standard heap-dump analyzer: leaks suspect report, dominator tree, OQL queries, and path-to-gc-roots to pinpoint what's holding onto memory.
open-sourceEPL-2.0
GCViewer
A Java tool that parses GC log files into charts of pause times, throughput and heap usage; the classic quick look at garbage collection behavior.
open-sourceLGPL-2.1
GCeasy
Upload a GC log and get an instant, annotated analysis — pause stats, throughput, latency percentiles, and likely tuning recommendations — hosted in the browser.
managedFree tier + paid
Java Agent for Memory Measurements (JAMM)
A Java agent that measures actual in-memory size of objects, including JVM per-object overhead, when you need byte-accurate 'how big is this really' answers.
open-sourceApache-2.0
JOL (Java Object Layout)
OpenJDK's tool for measuring and printing the on-heap layout and footprint of objects and arrays, useful for understanding alignment and padding costs.
open-sourceGPLv2 w/ CE
VisualGC
The classic VisualVM plugin showing live generations, spaces, and GC counts for a JVM; still the clearest quick view of how a collector is ticking.
freewareGPLv2 + CE

In-depth guides in this category

Eclipse MAT
Eclipse MAT tutorial: load a heap dump, run the Leak Suspects report, use the Dominator Tree and OQL, and find what holds objects to GC roots.
GC Log Analysis
GC log analysis guide: enable GC logging on modern JDKs, read -Xlog:gc output, and analyze pause/throughput with GCViewer and gceasy.