Add-ons are small pieces of code that you (or your administrator) can install into y Atlassian application to enhance or change its functionality. Add-ons can also be remotely contained web applications that integrate into Atlassian Cloud instances. You can enable, disable, install, and uninstall add-ons anytime from the administration pages of your Atlassian product.
Add-ons change the way your Atlassian application behaves. Even though add-ons are designed to enhance your product, there can be unintended effects. When you use or install add-ons, you do so at your own risk. Third-party add-ons aren't supported by Atlassian.
The Marketplace sells add-ons written by both Atlassian and the broader Atlassian community. You can even write one yourself.