SEO and 404 error redirection

Question

Recently I've removed some products and categories from my Magento store and that generated some many 404 errors as the pages where in the research index and now they doesn't exist anymore.

I was thinking about developing/using a module that takes the request to the store when they should give 404 and use keywords from the request URL to build a search query on the website so the customers doesn't get stop by a dead link.

But the question is: will that kill my SEO? How does Google, for instance, couple with the 404 error suppression? As anyone else encountered this problem and tried something like this?

Since the operation will take quite some time, I would like some feedback before going into this road.

As now, I only know that redirecting 404 error to the homepage or another page is bad as it keeps dead links alive, but redirecting with a criteria will have the same "zombifing" effect?

Answer 1

In their SEO guide Google recommends building a nice custom 404 page for your case (do not forget to return 404 status code).

Abstractly quoting: "A good custom 404 page will help people find the information they're looking for, as well as providing other helpful content and encouraging them to explore your site further."

Google's recommendations about 404 pages are available here. Also do not forget to check their starter SEO guide in the "Best Practices" chapter.

I would just try to follow the recommendations as close as possible.

Good luck!