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By default, all Checkly runners (the isolated environments where checks execute) run with their time zone set to UTC, regardless of the locations used in your checks.

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Resource limitations

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Browser and Multistep Checks

Browser and Multistep checks can use up to 2.7 GiB of memory and 1678m milli-CPU units. This limit applies to all processes spawned by the check, including the browser, the test framework, and the test code itself. The limit is enforced by the runner and is not configurable.
When the memory limit is exceeded, the check will automatically fail with a relevant error message, for example: Your check has reached the maximum memory usage of 2.7 GiB.

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Playwright Check Suites

Playwright Check Suites run in a custom dependencies environment. Playwright Check Suites can use up to 6.8 GiB of memory and 33000m milli-CPU units.
  • Node.js version: v22
  • Execution limit: 30 minutes per check run
Playwright Check Suites install dependencies from your package.json to create the runtime environment. Learn more about using custom dependencies.
To take advantage of the available CPU cores, configure workers in your playwright.config.ts:
workers: process.env.CHECKLY ? 4 : undefined,

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Built-in Node.js modules

The following standard Node modules are included and can be used as normal, e.g. 
import * as path from 'path'
  • assert
  • buffer
  • crypto
  • dns
  • fs (partial, we have restricted some file system operations for security reasons)
  • path
  • querystring
  • readline
  • stream
  • string_decoder
  • timers
  • tls
  • url
  • util
  • zlib
See the built-in module documentation on the official Node.js site (please see below which runtime includes what NodeJS version):

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NPM packages

These are the currently available runtimes and the included external NPM dependencies.
The packages below are included for setup and teardown scripts as well, with the exclusion of fs, Playwright and mocha.

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2025.04

Node.js Version: v22.11.0 The main update is Playwright 1.51.1. The Node.js version is v22.11.0.

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2024.09

Node.js Version: v18.20.3 The main update is Playwright 1.48.2. The Node.js version is v18.20.3. New dependencies are @clerk/testing, mailosaur, gaxios, @kubernetes/client-node and mysql.

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2024.02

Node.js Version: v18.20.3 The main update is Playwright 1.42.1. The Node.js version is v18.20.3. New dependencies are @opentelemetry/exporter-metrics-otlp-grpc, @opentelemetry/sdk-metrics, chai-json-schema, pdf2json, protobufjs, long and the nice-grpc family.

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2023.09

Node.js Version: v18.20.3 The main updates are Playwright 1.38.1 and the addition of ethers 6.7.1, prisma 5.1.1, zod 3.22.2, @t3-oss/env-nextjs 0.6.1 and @xmldom/xmldom 0.8.10. The Node.js version is v18.20.3.

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2023.02

Node.js Version: v16.20.2 The main updates are Playwright 1.32.1, faker 7.6.0 and the addition of date-fns 2.29.3 and ws 8.13.0. We are dropping support for Mocha.

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2022.10

Node.js Version: v16.20.2 The main updates are Playwright 1.28.0, Node.js v16.20.2 and Typescript support. We are dropping support for Puppeteer.