---

id: 83

slug: "jfr-profiling"

title: "JFR for profiling"

category: "tooling"

difficulty: "intermediate"

jdkVersion: "9"

oldLabel: "Java 8"

modernLabel: "Java 9+"

oldApproach: "External Profiler"

modernApproach: "Java Flight Recorder"

oldCode: |-

// Install VisualVM / YourKit / JProfiler

// Attach to running process

// Configure sampling

// Export and analyze

// External tool required

modernCode: |-

// Start with profiling enabled

$ java -XX:StartFlightRecording=

filename=rec.jfr MyApp

// Or attach to running app:

$ jcmd <pid> JFR.start

summary: "Profile any Java app with the built-in Flight Recorder — no external tools."

explanation: "Java Flight Recorder (JFR) is a low-overhead profiling tool built into\

\ the JVM. It captures events for CPU, memory, GC, I/O, threads, and custom events\

\ with minimal performance impact (~1%)."

whyModernWins:

- icon: "🆓"

title: "Built-in"

desc: "No external profiler to install or license."

- icon: "⚡"

title: "Low overhead"

desc: "~1% performance impact — safe for production."

- icon: "📊"

title: "Rich events"

desc: "CPU, memory, GC, threads, I/O, locks, and custom events."

support:

state: "available"

description: "Widely available since JDK 9/11 (open-sourced in 11)"

prev: "tooling/multi-file-source"

next: "tooling/compact-object-headers"

related:

- "tooling/multi-file-source"

- "tooling/jshell-prototyping"

- "tooling/single-file-execution"

docs:

- title: "JDK Flight Recorder"

href: "https://docs.oracle.com/en/java/javase/25/docs/specs/man/jfr.html"

- title: "Flight Recorder API (JEP 328)"

href: "https://openjdk.org/jeps/328"