Rewrite URL when migrating an eCommerce website to Magento

I recently worked on an interesting project for migrating from an old ASP.NET eCommerce site to the latest version of Magento 2 open source (2.1.9).

A common request is, they want to redirect permanently their old product URL to a new one to the new URL under Magento 2 URL structure.

I suppose that they need to redirect product with old URL:

/productdetail.aspx?ID=99 to /this-is-a-migrated-magento-product-url.html


You may think that it is just simply adding custom URL redirection in Magento URL Rewrite management like the picture below

But doing so would bring this URL  to a 404 page.

I did a simple trick with .htaccess

RewriteCond %{REQUEST_URI}  ^/productdetail\.aspx$
RewriteCond %{QUERY_STRING} ^ID=([0-9]*)$
RewriteRule ^(.*)$ [R=301,L]


and then, I will add this custom url to magento backend


After that, when visiting

It will be redirected to

I really hope my quick tip will save you guys time for finding a solution to saving the website SEO ranking after migration and avoiding users with annoying 404 errors.