# marmelab/gremlins.js

Monkey testing library for web apps and Node.js

Repository: https://github.com/marmelab/gremlins.js
Canonical: https://ross.abutalabs.com/products/gremlinsjs
Homepage: https://marmelab.com/blog/2020/06/02/gremlins-2.html
Language: JavaScript
License: MIT
License Family: permissive
Topics: test, fuzz-testing, frontend
Last push: 2023-03-06T22:42:44+00:00

## Health v2 (maintenance only)
Score: 23/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 0, release rhythm 8, longevity 100
- inputs: {"age_days": 4699, "days_push": 1276, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 9091, forks 424 (observed 2026-08-28T04:10:28.312456+00:00)

## What it is
gremlins.js is a JavaScript monkey testing library for Node.js and the browser that unleashes random user-like actions (clicking, typing, scrolling, form filling, touching) on a web app to test its robustness. It includes 'mogwai' watchers that monitor console errors and frame rates to detect errors, performance problems, and memory leaks.

## Use cases
- stress test a web app with random clicks and typing
- detect memory leaks in frontend JavaScript
- find unhandled errors in a web application
- run chaos/monkey testing in Cypress or Playwright
- check robustness of an HTML5 app before release

## When to choose
- you want randomized, unscripted stress testing of a browser-based frontend
- you need to surface crashes, console errors, or performance degradation from unpredictable user behavior
- you want a lightweight library that integrates with Cypress or Playwright

## When to avoid
- you need deterministic, assertion-based unit or e2e tests
- you are testing non-browser backend code
- you need actively maintained tooling with frequent updates

## Facets
- artifact type: library
- maturity: maintenance
- function: testing, fuzzing, benchmarking
- domain: testing, web-development, frontend, developer-tools
- platform: browser
- tags: monkey-testing, chaos-testing, stress-testing, bookmarklet, cypress, playwright, nodejs, javascript

## Member repositories
- marmelab/gremlins.js (main) score 23

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:10:28.312456+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 2026-08-29T17:23:59.669386+00:00, confidence not recorded.
  - readme: https://github.com/marmelab/gremlins.js (fetched 2026-08-28T04:10:28.312456+00:00, sha 6d3f85fb511b)
  - homepage: https://marmelab.com/blog/2020/06/02/gremlins-2.html (fetched 2026-08-29T08:24:05.458232+00:00, sha 08fa7c667aaf)
  - registry_npm: https://registry.npmjs.org/gremlins.js (fetched 2026-08-29T08:24:05.467954+00:00, sha f0fa97a067ce)
- Data as of 2026-08-30T08:39:29.467469+00:00.