memlab

library2.0.1jsnpmunverified

MemLab is an end-to-end testing and analysis framework for identifying JavaScript memory leaks and optimization opportunities. Version 2.0.1 is the latest stable release, actively maintained by Meta. It provides automated browser memory leak detection using Puppeteer, a heap snapshot analysis API for Node.js/Electron/Hermes, and CLI tools for memory debugging. Key differentiators: supports custom leak detectors, object-oriented heap traversing, and integrates with unit testing. MemLab goes beyond simple heap dump analysis by automatically comparing snapshots and filtering leaks with retainer traces.

testing observability

npm install memlab

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · MEMLAB

memlab

testingjavascriptv2.0.1

Install

—

Import

—

Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

memlab

✓ import memlab from 'memlab'

✗ const memlab = require('memlab')

MemLab is ESM-only since v2; CJS require will fail.

IScenario

✓ import { IScenario } from 'memlab'

✗ import IScenario from 'memlab'

Type-only export; must use named import.

takeHeapSnapshot

✓ import { takeHeapSnapshot } from 'memlab'

✗ import takeHeapSnapshot from 'memlab'

Named export for heap snapshot API.

Demonstrates using MemLab's programmatic API to define a scenario and run browser memory leak detection.

import memlab from 'memlab'; import fs from 'fs'; // Define a scenario as an object with url, action, back functions const scenario = { url: () => 'https://example.com', async action(page) { await page.click('button#load-more'); }, async back(page) { await page.click('button#reset'); } }; async function runLeakDetection() { // Run leak detection with default options const result = await memlab.run(scenario); console.log(`Leaks found: ${result.leaks.length}`); for (const leak of result.leaks) { console.log(`Retained size: ${leak.retainedSize}`); } } runLeakDetection().catch(console.error);

memlab --version

Debug

Known issues

breakingMemLab v2 drops CommonJS support; only ESM imports work.

fix

Use import syntax instead of require().

affects: >=2.0.0

breakingThe CLI 'memlab run' command changed its argument from --browser to --runner in v2.

fix

Use '--runner puppeteer' instead of '--browser puppeteer'.

affects: >=2.0.0 <2.0.1

deprecatedFunction 'createBrowserlessScenario' is deprecated in v2. Use the object-based scenario format.

fix

Define scenario as {url, action, back} instead.

affects: >=2.0.0

gotchaHeap snapshot files can be very large (multiple GB). Ensure sufficient disk space.

fix

Monitor disk usage; consider using --max-snapshots option to limit files.

affects: >=1.0.0

gotchaMemLab runs Puppeteer in headless mode by default; some sites may require full browser.

fix

Set headless: false in Puppeteer launch options within scenario.

affects: >=1.0.0

gotchaRetainer traces may be unavailable if minified code is served; use source maps.

fix

Ensure the website serves non-minified code or source maps for readable traces.

affects: >=1.0.0

Errors

Common errors & fixes

TypeError: memlab.run is not a function

Using require() instead of import for ESM-only package.

fix

Replace const memlab = require('memlab') with import memlab from 'memlab'.

Error: Cannot find module 'puppeteer'

Puppeteer is an optional peer dependency not installed.

fix

Run npm install --save-dev puppeteer to install it.

Error: The 'back' action must be a function

Missing or invalid 'back' function in scenario object.

fix

Define an async 'back' function that returns to the pre-action state.

Error: EACCES: permission denied, mkdir '/tmp/memlab'

MemLab uses /tmp for snapshot storage; may lack permissions.

fix

Override work directory with memlab.setWorkDir('/custom/path') or run with sudo.

Upgrade

Version history

2.0.1latest on npm

Audit

Dependencies

puppeteeroptionalUsed for browser automation in leak detection scenarios

Agent activity

26 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/facebook/memlab ↗

packagehttps://www.npmjs.com/package/memlab ↗

homepagehttps://facebook.github.io/memlab/ ↗