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When routes not exists what we are looking for in web application, then we can handle this via 404 error page i.e page not found. Inside this article we will discuss such type of concept in CodeIgniter 4.
We will create a custom 404 page in CodeIgniter 4. We will override the default 404 page of CodeIgniter 4 application.
Note*: For this article, CodeIgniter v4.1 setup has been installed. May be when you are seeing, version will be updated. CodeIgniter 4.x still is in development mode.

Let’s get started.
Download & Install CodeIgniter 4 Setup
We need to download & install CodeIgniter 4 application setup to system. To set application we have multiple options to proceed. Here are the following ways to download and install CodeIgniter 4 –
- Manual Download
- Composer Installation
- Clone Github repository of CodeIgniter 4
Complete introduction of CodeIgniter 4 basics – Click here to go. After going through this article you can easily download & install setup.
Here is the command to install via composer –
$ composer create-project codeigniter4/appstarter codeigniter-4
Assuming you have successfully installed application into your local system.
Settings Environment Variables
When we install CodeIgniter 4, we have env file at root. To use the environment variables means using variables at global scope we need to do env to .env
Open project in terminal
$ cp env .env
Above command will create a copy of env file to .env file. Now we are ready to use environment variables.
CodeIgniter starts up in production mode by default. Let’s do it in development mode. So that while working if we get any error then error will show up.
# CI_ENVIRONMENT = production // Do it to CI_ENVIRONMENT = development
Now application is in development mode.
Application 404 Route Settings
Open Routes.php from /app/Config. Inside this file search for set404Override().
$routes->set404Override();
When we open any routes which is not configured in application, then getting 404 error page. By default this is 404 error page template of CodeIgniter 4.

This default layout is loaded from /app/Views/errors/html/error_404.php
We need to change this layout.
404 Custom Layout Setup
To create a custom layout for 404 error page, we need to use the same block of code what we have seen above. We need to add a callback function into it to return template view file.
Use a Static Message
Example
Let’s set a static message for getting 404 error in application.
$routes->set404Override(function() { echo "<h3>Page not found - Custom Message</h3>"; });
Whenever we get any 404 then this static message will be rendered. No default layout will be used.
Use a View Template File
Let’s create a view file 404.php inside /app/Views.
Open 404.php and write this piece of code into it.
<!doctype html> <html> <head> <title>404 Page Not Found</title> <style> body { width: 99%; height: 100%; background-color: #d1486894; color: #fff; font-family: sans-serif; } div { position: absolute; width: 400px; height: 300px; z-index: 15; top: 45%; left: 50%; margin: -100px 0 0 -200px; text-align: center; } h1, h2 { text-align: center; } h1 { font-size: 60px; margin-bottom: 10px; border-bottom: 1px solid white; padding-bottom: 10px; } h2 { margin-bottom: 40px; } a { margin-top: 10px; text-decoration: none; padding: 10px 25px; background-color: #fff; color: black; margin-top: 20px; border-radius: 10px; } </style> </head> <body> <div> <h1>404</h1> <h2>Page not found</h2> <a href='<?= base_url() ?>'>Back to Site</a> </div> </body> </html>
Setting template to 404 override method
$routes->set404Override(function() { return view("404"); });
Now, when we open any application route which don’t really exists then we will get custom 404 page what we created.

We hope this article helped you to learn Create Custom 404 Page in CodeIgniter 4 | Page Not Found in a very detailed way.
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