# Library functions available for canary scripts
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CloudWatch Synthetics includes several built-in classes and functions that you can call when writing Node.js scripts to use as canaries.

Some apply to both UI and API canaries. Others apply to UI canaries only. A UI canary is a canary that uses the `getPage()` function and uses Puppeteer as a web driver to navigate and interact with webpages.

**Note**  
Whenever you upgrade a canary to use a new version of the the Synthetics runtime, all Synthetics library functions that your canary uses are also automatically upgraded to the same version of NodeJS that the Synthetics runtime supports.

**Topics**
+ [Library functions available for Node.js canary](Library_function_Nodejs.md)
+ [Library functions available for Java canary](CloudWatch_Synthetics_Canaries_Java.md)
+ [Library functions available for Node.js canary scripts using Playwright](CloudWatch_Synthetics_Canaries_Nodejs_Playwright.md)
+ [Library functions available for Node.js canary scripts using Puppeteer](CloudWatch_Synthetics_Canaries_Library_Nodejs.md)
+ [Library functions available for Python canary scripts using Selenium](CloudWatch_Synthetics_Canaries_Library_Python.md)