.htaccess

DirectoryIndex index.php

<IfModule mod_negotiation.c>
    Options -MultiViews
</IfModule>

<IfModule mod_rewrite.c>
    RewriteEngine On

    RewriteCond %{REQUEST_URI} ^/$
    Rewriterule ^(.*)$ /app/index.html [L,R=301]

    RewriteRule ^(app) - [L]

    # Determine the RewriteBase automatically and set it as environment variable.
    RewriteCond %{REQUEST_URI}::$0 ^(/.+)/(.*)::\2$
    RewriteRule .* - [E=BASE:%1]

    # Sets the HTTP_AUTHORIZATION header removed by Apache
    RewriteCond %{HTTP:Authorization} .+
    RewriteRule ^ - [E=HTTP_AUTHORIZATION:%0]

    # Redirect to URI without front controller to prevent duplicate content
    RewriteCond %{ENV:REDIRECT_STATUS} =""
    RewriteRule ^index\.php(?:/(.*)|$) %{ENV:BASE}/$1 [R=301,L]

    # If the requested filename exists, simply serve it.
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteRule ^ %{ENV:BASE}/index.php [L]
</IfModule>

<IfModule !mod_rewrite.c>
    <IfModule mod_alias.c>
        # When mod_rewrite is not available, temporary redirect of
        # the start page to the front controller explicitly so that the website
        # and the generated links can still be used.
        RedirectMatch 307 ^/$ /index.php/
        # RedirectTemp cannot be used instead
    </IfModule>
</IfModule>