Simple Triggers

Triggers let Apps Script run a function automatically when a certain event, like opening a document, occurs. Simple triggers are a set of reserved functions built into Apps Script, like the function onOpen(e), which executes when a user opens a Google Docs, Sheets, or Forms file. Installable triggers offer more capabilities than simple triggers but must be activated before use. For both types of triggers, Apps Script passes the triggered function an event object that contains information about the context in which the event occurred.

Getting started

To use a simple trigger, simply create a function that uses one of these reserved function names:

onOpen(e) runs when a user opens a spreadsheet, document, or form that he or she has permission to edit.
onEdit(e) runs when a user changes a value in a spreadsheet.
onInstall(e) runs when a user installs an add-on.
doGet(e) runs when a user visits a web app or a program sends an HTTP GET request to a web app.
doPost(e) runs when a program sends an HTTP POST request to a web app.

The e parameter in the function names above is an event object that is passed to the function. The object contains information about the context that caused the trigger to fire, but using it is optional.

Restrictions

Because simple triggers fire automatically, without asking the user for authorization, they are subject to several restrictions:

The script must be bound to a Google Sheets, Docs, or Forms file.
They do not run if a file is opened in read-only (view or comment) mode.
They cannot access services that require authorization. For example, a simple trigger cannot send an email because the Gmail service requires authorization, but a simple trigger can translate a phrase with the Language service, which is anonymous.
They can modify the file they are bound to, but cannot access other files because that would require authorization.
They may or may not be able to determine the identity of the current user, depending on a complex set of security restrictions.
They cannot run for longer than 30 seconds.
In certain circumstances, add-ons for Google Sheets, Docs, and Forms run their onOpen(e) and onEdit(e) simple triggers in a no-authorization mode that presents some additional complications. For more information, see the guide to the add-on authorization lifecycle.

These restrictions do not apply to doGet() or doPost().

`onOpen()`

The onOpen() trigger runs automatically when a user opens a spreadsheet, document, or form that he or she has permission to edit. (The trigger does not run when responding to a form, only when opening the form to edit it.) onOpen() is most commonly used to add custom menu items to Google Sheets, Docs, or Forms.

function onOpen() {
  // Add a custom menu to the spreadsheet.
  SpreadsheetApp.getUi() // Or DocumentApp or FormApp.
      .createMenu('Custom Menu')
      .addItem('First item', 'menuItem1')
      .addToUi();
}

`onEdit()`

The onEdit() trigger runs automatically when a user changes the value of any cell in a spreadsheet. Most onEdit() triggers use the information in the event object to respond appropriately. For example, the onEdit(e) function below sets a comment on the cell that records the last time it was edited.

function onEdit(e){
  // Set a comment on the edited cell to indicate when it was changed.
  var range = e.range;
  range.setNote('Last modified: ' + new Date());
}

`onInstall()`

The onInstall() trigger runs automatically when a user installs an add-on. The most common use of onInstall() is simply to call onOpen() to add custom menus. After all, when an add-on is installed, the file is already open, and thus onOpen() will not run on its own unless the file is reopened.

function onInstall(e) {
  onOpen(e);
}

`doGet()` and `doPost()`

The doGet() trigger runs automatically when a user visits a web app or a program sends an HTTP GET request to a web app. doPost(e) runs when a program sends an HTTP POST request to a web app. These triggers are demonstrated more in the guides to web apps, HTML service, and Content service. Note that doGet() and doPost() are not subject to the restrictions listed above.

Available types of triggers

If the restrictions on simple triggers keep them from meeting your needs, an installable trigger might work instead. The table below summarizes which types of triggers are available for each type of event. For example, Google Sheets, Forms, and Docs all support simple open triggers, but only Sheets and Forms support installable open triggers.

Event	Simple triggers	Installable triggers
Open	Sheets Forms* Docs `function onOpen(e)`	Sheets Forms* Docs
Edit	Sheets `function onEdit(e)`	Sheets
Install	Sheets Forms Docs `function onInstall(e)`
Change		Sheets
Form submit		Sheets Forms
Time-driven (clock)		Sheets Forms Docs Sites Standalone
Get	Sites Standalone `function doGet(e)`
Post	Sites Standalone `function doPost(e)`