Custom redirects are redirects that are not covered on the Article Redirects feature, learn more at How to Create Article/URL Redirects. For instance:

1. Redirects from valid URLs on your KB;
2. Redirects based on search parameters or event listeners;

In order to redirect users before the page is fully loaded, place the code in the Main Layout file, inside the HEAD tag.

Example

<script>
if (location.pathname === "/en_US") {
    location.href = "/en_GB";
}
</script>

In this example, we created a redirect from the English (US) language section to the English (UK) section. You might want to use liquid tags to create more robust/complex redirects, learn more at Shopify/Liquid Variables and Objects Reference.