|Initial release||August 19, 2009|
|Type||Web application framework, scripting framework|
In March 2014, Google introduced add-ons for Docs and Sheets (soon followed by Forms). The add-on stores let users add extra features to Google editors, such as mail-merging, workflows, and diagrams builders. All add-ons are either 100% built with Apps Script or simply use Apps Script to display a UI in the Google editors while relying on an external back-end to perform some tasks. For example, MailChimp, a mail-merging tool, has an add-on for Google Docs that communicates with MailChimp platform to send emails.
Before add-ons, it was possible to publish scripts for Google Sheets in the Script Gallery. When users installed scripts through this gallery, a copy of the Apps Script code was installed on the user's Sheet. With add-ons, the source code is not visible to the end user and everyone is using the latest version published by the developer. This new approach makes it easier to support existing code and helped convince several companies, such as MailChimp or LucidChart to invest in Apps Script.
As part of the add-ons release, Google also introduced a UI Style Guide and CSS package to help developers built add-ons that integrate smoothly into the editors. Each add-on is also reviewed by Google before its publication and developers can benefit from advice from Googlers to provide a better user experience. It is not possible to embed ads in add-ons but it is possible to monetize them.
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