There is an issue on Yii2 to redirecting / urls to /frontend/web.
In other words we need a way to hidden /frontend/web from addresses

Let's do it:

1- Create .htaccess file on the root directory with this content

Options -Indexes

<IfModule mod_rewrite.c> 
  RewriteEngine on
  
  RewriteCond %{REQUEST_URI} !^public
  RewriteRule ^(.*)$ frontend/web/$1 [L] 
</IfModule>

# Deny accessing below extensions
<Files ~ "(.json|.lock|.git)">
Order allow,deny
Deny from all
</Files>

# Deny accessing dot files
RewriteRule (^\.|/\.) - [F]

2- Create .htaccess file in frontend/web with the below contents

RewriteEngine on

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d 

RewriteRule . index.php

3- Now, we should play a little with frontend config of framework
You must open the frontend/config/main.php file and set $baseUrl for \yii\web\Request and \yii\web\urlManager.
$baseUrl is the url your application point to. if you host your application in the root directory of www you may set the $baseUrl to '/'

For another example if you are developing a blog system and your application hosted in www/blog you must set the baseUrl to '/blog'

<?php
$params = array_merge(
    require(__DIR__ . '/../../common/config/params.php'),
    require(__DIR__ . '/../../common/config/params-local.php'),
    require(__DIR__ . '/params.php'),
    require(__DIR__ . '/params-local.php')
);


return [
    'id' => 'app-frontend',
    'basePath' => dirname(__DIR__),
    'bootstrap' => ['log'],
    'controllerNamespace' => 'frontend\controllers',
	
    'components' => [
		
		'request' => [
			'baseUrl' => '/',
		],
		
        'user' => [
            'identityClass' => 'common\models\User',
            'enableAutoLogin' => true,
        ],
		
        'log' => [
            'traceLevel' => YII_DEBUG ? 3 : 0,
            'targets' => [
                [
                    'class' => 'yii\log\FileTarget',
                    'levels' => ['error', 'warning'],
                ],
            ],
        ],
		
        'errorHandler' => [
            'errorAction' => 'site/error',
        ],
		
		'urlManager' => [
			'baseUrl' => '/',
			'enablePrettyUrl' => true,
			'showScriptName' => false,
			'rules' => []
		]
    ],
    'params' => $params,
];

Soft Way ¶

If you not sure where your application will host, you must do it in pragmatically way. for this purpose we change the config file as below

<?php
$params = array_merge(
    require(__DIR__ . '/../../common/config/params.php'),
    require(__DIR__ . '/../../common/config/params-local.php'),
    require(__DIR__ . '/params.php'),
    require(__DIR__ . '/params-local.php')
);

use \yii\web\Request;
$baseUrl = str_replace('/frontend/web', '', (new Request)->getBaseUrl());

return [
    'id' => 'app-frontend',
    'basePath' => dirname(__DIR__),
    'bootstrap' => ['log'],
    'controllerNamespace' => 'frontend\controllers',
	
    'components' => [
		
		'request' => [
			'baseUrl' => $baseUrl,
		],
		
        'user' => [
            'identityClass' => 'common\models\User',
            'enableAutoLogin' => true,
        ],
		
        'log' => [
            'traceLevel' => YII_DEBUG ? 3 : 0,
            'targets' => [
                [
                    'class' => 'yii\log\FileTarget',
                    'levels' => ['error', 'warning'],
                ],
            ],
        ],
		
        'errorHandler' => [
            'errorAction' => 'site/error',
        ],
		
		'urlManager' => [
			'baseUrl' => $baseUrl,
			'enablePrettyUrl' => true,
			'showScriptName' => false,
			'rules' => []
		]
    ],
    'params' => $params,
];

As you see above we use \yii\web\Request to find $baseUrl of application. but because the returned $baseUrl contains /frontend/web we remove it

use \yii\web\Request;
$baseUrl = str_replace('/frontend/web', '', (new Request)->getBaseUrl());

enjoy !