You have to config the **.htaccess** file
RewriteEngine On RewriteCond %{SERVER_PORT} 80 RewriteRule ^(.*)$ https://www.example.com/$1 [R,L]
Replace example.com to your domain
This is how your current .htaccess file would be


<IfModule mod_rewrite.c> RewriteEngine On RewriteBase / RewriteCond %{REQUEST_URI} ^system.* RewriteRule ^(.*)$ /index.php?/$1 [L] RewriteCond %{REQUEST_URI} ^application.* RewriteRule ^(.*)$ /index.php?/$1 [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule ^(.*)$ index.php?/$1 [L] </IfModule> <IfModule !mod_rewrite.c> ErrorDocument 404 /index.php </IfModule> RewriteEngine On RewriteCond %{SERVER_PORT} 80 RewriteRule ^(.*)$ https://www.example.com/$1 [R,L]

> Alterative 2 using hooks to redirect no need change .htaccess
Config changes :- Go to **“application/config/config.php”** and enable or set hooks to true.
$config['enable_hooks'] = TRUE;
create a new file named hooks.php in **“application/config/hooks.php”** and add below code in **hooks.php**:
$hook['post_controller_constructor'][] = array( 'function' => 'redirect_ssl', 'filename' => 'ssl.php', 'filepath' => 'hooks' );
Now create a new directory with named “hooks” under application directory and then create new file named “ssl.php” in **“application/hooks/ssl.php”** and add below code to “ssl.php” :
function redirect_ssl() { $CI =& get_instance(); $class = $CI->router->fetch_class(); $exclude = array('client'); // add more controller name to exclude ssl. if(!in_array($class,$exclude)) { // redirecting to ssl. $CI->config->config['base_url'] = str_replace('http://', 'https://', $CI->config->config['base_url']); if ($_SERVER['SERVER_PORT'] != 443) redirect($CI->uri->uri_string()); } else { // redirecting with no ssl. $CI->config->config['base_url'] = str_replace('https://', 'http://', $CI->config->config['base_url']); if ($_SERVER['SERVER_PORT'] == 443) redirect($CI->uri->uri_string()); } }

Please Check this may help
Config changes :- Go to “application/config/config.php” and enable or set hooks to true.
$config['enable_hooks'] = TRUE;
create a new file named hooks.php in “application/config/hooks.php” and add below code in hooks.php:-
$hook['post_controller_constructor'][] = array( 'function' => 'redirect_ssl', 'filename' => 'ssl.php', 'filepath' => 'hooks' );
Now create a new directory with named “hooks” under application directory and then create new file named “ssl.php” in “application/hooks/ssl.php” and add below code to “ssl.php” :-
function redirect_ssl() { $CI =& get_instance(); $class = $CI->router->fetch_class(); $exclude = array('client'); // add more controller name to exclude ssl. if(!in_array($class,$exclude)) { // redirecting to ssl. $CI->config->config['base_url'] = str_replace('http://', 'https://', $CI->config->config['base_url']); if ($_SERVER['SERVER_PORT'] != 443) redirect($CI->uri->uri_string()); } else { // redirecting with no ssl. $CI->config->config['base_url'] = str_replace('https://', 'http://', $CI->config->config['base_url']); if ($_SERVER['SERVER_PORT'] == 443) redirect($CI->uri->uri_string()); } }