Triggers (onEdit, onOpen) in Google Sheets - Step-by-Step Guide

Introduction

Triggers in Google Sheets let you run a script automatically when you open a sheet or edit a cell. This helps you automate tasks without clicking buttons.

When you want to show a welcome message every time someone opens the sheet

When you want to check data or update values automatically after a user changes a cell

When you want to log changes made to the sheet without manual effort

When you want to send notifications after edits happen

When you want to prepare or reset the sheet layout each time it opens

Steps

Step 1: Open

- Google Sheets file

Your spreadsheet is visible and ready

Step 2: Click

- Extensions menu > Apps Script

The Apps Script editor opens in a new tab

Step 3: Type

- Code editor

You enter a function named onOpen or onEdit

💡 Use exact function names: onOpen() or onEdit(e) for automatic triggers

Step 4: Write

- Inside the function

Your script runs automatically when the event happens

💡 For example, onOpen runs when the sheet opens; onEdit runs after any cell edit

Step 5: Save

- Apps Script editor (File > Save or Ctrl+S)

Your script is saved and ready to run

Step 6: Return

- Google Sheets tab

Your script triggers will run automatically on open or edit

Before vs After

Before

No script runs automatically when opening or editing the sheet

After

A welcome message appears on open or a cell value updates automatically after editing

Settings Reference

Simple Triggers

📍 Apps Script editor, function names onOpen() and onEdit(e)

Run code automatically when the sheet opens or a cell is edited

Default: No triggers run until you add these functions

Installable Triggers

📍 Apps Script editor > Triggers (clock icon) > Add Trigger

Create triggers with more permissions and options than simple triggers

Default: No triggers installed by default

Common Mistakes

Naming the function something other than onOpen or onEdit

Simple triggers only run if the function name is exactly onOpen or onEdit

Use the exact function names onOpen() or onEdit(e) for automatic triggers

Expecting onEdit to run without the event object parameter

onEdit needs the event object (e) to know what was edited

Define onEdit with a parameter like onEdit(e) to access edit details

Trying to run scripts that require authorization inside simple triggers

Simple triggers have limited permissions and cannot perform some actions

Use installable triggers from the Triggers menu for scripts needing more permissions

Summary

Triggers run scripts automatically when you open or edit a Google Sheet

Use onOpen() to run code on sheet open and onEdit(e) to run code after edits

Simple triggers have limits; use installable triggers for advanced needs