Redirecting urls from old website to new squarespace website

Hi, I'm building a new site in Squarespace for a client who's old site is a C Panel/ html website.

The old website has numerous pages which customers have he link to to access content (videos) they had purchased to be able to replay/ rewatch.

I recreated those pages in the new website in a Membership area so going forward a customer will create an account and then have access in their portal to access any videos they had purchased.

The new website will have the same domain as the current old website. The old website will then have a modified domain for a period of time (6 months or so).

My question is: What is the most efficient way (and easiest for the customer) to redirect those old URL's/links to the new pages/ Membership area? There are hundreds of customers and we'd like to avoid having to contact each one.

I realize that the customers will need to create an account & password on the new website to access the Membership portal.

I received one suggestion of having a 404 page on the old website simply direct them to the new website.

Any and all ideas gratefully welcomed 🙂

-Janet

In addition to an informative 404 page, I'd highly recommend getting a URL Report from a service like Screaming Frog SEO Spider for both the old site and the new site, and then creating 301 redirects for each URL that is changing. It's a pain, yes, if there are lots of pages, but redirects will ensure that the URLs continue to work after you switch everything. Simply setting up a 404 page could cause members to get annoyed that they can't find what they were looking for easily. 

Under Settings, then Developer Tools, then URL Mappings, you can add 301 Redirects. A typical redirect looks like the following:

/old-back-half-url -> /new-back-half-url 301

I have a Screaming Frog account and I've done tons of these URL reports before, so I'd be happy to help you if you need it or have questions. Feel free to reach out.