Which file in opencart is responsible for processing the url request?

Question

opencart

There was a need to intercept the url sent from the product page and partially change it. I can't determine which file in opencart is responsible for parsing the url and returning a 404 or 200 error. seo_url is enabled. I would be grateful for any hints.

Answer 1

Depending on the used seo url engine:
catalog/controller/startup/seo_url.php
catalog/controller/startup/seo_pro.php
404 can be thrown anywhere.

$this->response->addHeader($this->request->server['SERVER_PROTOCOL'] . ' 404 Not Found');