Free online Java thread dump analyzer — no signup

What the analyzer detects

The analyzer auto-detects the thread dump format, groups threads by pool and state and runs 15 detectors. The most sought-after problems:

• Deadlock — lock cycles between threads, including those already declared by the JVM.
• Pool exhaustion — every thread in a pool busy at once, with the queue growing.
• CPU spike — RUNNABLE threads clustered in hot methods: loops, catastrophic regex, heavy serialization.
• Thread leak — threads outside any pool that only grow — typically an executor never shut down.
• Lock contention — many BLOCKED threads fighting for the same monitor, with the holder identified.
• Virtual thread pinning — virtual threads (Loom) pinned to the carrier by synchronized blocks or native code.

Supported formats

The parser recognizes the format from the header and structure — you never have to tell it which JVM produced the dump.

• HotSpot — OpenJDK and Oracle JDK — the most common format, with a declared deadlock section.
• OpenJ9 — Eclipse/IBM — javacore.txt files, with memory diagnostics included.
• Azul Zing / Prime — close to HotSpot, with extensions for the C4 collector and the Falcon JIT.
• GraalVM — HotSpot-compatible in JIT mode; its own convention in native image.

Privacy and dump data

The first dump requires no signup. The file is processed only to generate the report, retention is limited and you control deletion. Retention and encryption details on the security.

Want to learn to read a dump by hand? Read the complete thread dump analysis guide.