1 rewrite or internal redirection cycle while internally redirecting to "/en/index.html"

can you modify try_files to try_files $uri /$1/index.html?$args =404;, restart nginx, and try again?

Not it gives 404 Not Found.

map $http_accept_language $accept_language { ~*^de de; ~*^fr fr; ~*^en en; } server { ... root /var/www/html/app/dist/app; ... if ($accept_language ~ "^$") { set $accept_language "en"; } 

according to your configuration, when you send requests to nginx with URL http://i18n.example.com, nginx will try to append language code (en/fr/de) according to Accept-Language HTTP header sent by your user agent. when there's no such header exists, nginx will by default append en language code.

 rewrite ^/$ /$accept_language permanent; location ~ ^/(fr|de|en) { try_files $uri /$1/index.html?$args; } 

nginx then does an internal redirect to http://i18n.example.com/<language code> and evaluates location ~ ^/(fr|de|en) successfully.

for example, let's use en language code, so then the internal redirect points to http://i18n.example.com/en.

using this URI and your try_files $uri /$1/index.html?$args configuration, nginx will try to access http://i18n.example.com/en and http://i18n.example.com/en/index.html?<argument>; which translates to /var/www/html/app/dist/app/en and /var/www/html/app/dist/app/en/index.html respectively.

if no such file exists, which is happening in your current situation, your location ~ ^/(fr|de|en) will be re-triggered again since there's two requests to /en. this will create redirection loop inside nginx and it'll break out from the loop by sending an error.

to solve this, either check if you have /var/www/html/app/dist/app/en/index.html file available and readable by nginx, or add =404 to your try_files configuration to let it gracefully fail as 404 error.