# openjdk/jol

https://openjdk.org/projects/code-tools/jol

Repository: https://github.com/openjdk/jol
Canonical: https://ross.abutalabs.com/products/jol
Language: Java
License: GPL-2.0
License Family: copyleft
Last push: 2026-01-21T16:31:45+00:00

## Health v2 (maintenance only)
Score: 61/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 63, release rhythm 35, longevity 100
- inputs: {"age_days": 2169, "days_push": 224, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_releases
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1088, forks 110 (observed 2026-08-28T04:03:32.449413+00:00)

## What it is
Java Object Layout (JOL) is a toolbox for analyzing object layout, memory footprint, and references inside JVMs. It uses Unsafe, JVMTI, and Serviceability Agent to decode actual object layouts more accurately than heap-dump-based tools.

## Use cases
- analyze java object memory layout
- measure object memory footprint in jvm
- inspect field layout and padding of a class
- find duplicate strings in a heap dump
- estimate object sizes under compressed oops
- debug memory overhead of java data structures

## When to choose
- you need precise JVM object layout and footprint data
- you are tuning memory usage of Java applications
- you want to understand object header and alignment behavior

## When to avoid
- you need general heap profiling rather than layout analysis
- you work outside the JVM ecosystem

## Facets
- artifact type: library
- maturity: active
- function: developer-tools, benchmarking, monitoring
- domain: developer-tools, performance
- platform: jvm, cli
- tags: object-layout, memory-footprint, jvm-internals, heap-analysis, serviceability-agent, jvm, memory-analysis

## Member repositories
- openjdk/jol (main) score 61

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:03:32.449413+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T06:49:22.493233+00:00, confidence not recorded.
  - readme: https://github.com/openjdk/jol (fetched 2026-08-28T04:03:32.449413+00:00, sha 6e2b92ddfb93)
- Data as of 2026-08-30T08:39:29.467469+00:00.