What happens to my old website when I get a new one?

When your new website goes live, the old one does not disappear by itself. Your domain is simply pointed at the new site, so customers stop seeing the old one, but the old site keeps sitting on its hosting account, and you keep paying for it, until you cancel. That is useful: it gives you a safety net for a few weeks. The things to be careful with are the pieces that may be tied to the old account, especially your email, and the domain itself, which you should never cancel.

The old site, the domain and the hosting are three different things

It helps to separate three ideas that usually get lumped together:

The domain is your web address, like yourbakery.com. It is registered at a registrar and renewed every year. Think of it as your phone number.
The hosting is the computer where your site's files live. It might be a hosting company, a builder like Wix or Squarespace, or your designer's server. Think of it as the phone itself.
The website is the pages, text and photos that live on that hosting.

A new website usually means new hosting. The domain stays the same; it just gets pointed at the new hosting, the way you can move your phone number to a new phone. Can I keep my website address when I redesign? explains the pointing in detail.

What happens on switch day

When the domain's settings are changed to point at the new site:

Over the next few minutes to a day, visitors start seeing the new site at your usual address. The change spreads gradually across the internet, so for a short while some people may still see the old one.
The old site is still on its hosting, reachable only through the hosting company's own temporary address, if at all. Customers no longer land on it.
Your email keeps working, provided whoever made the change left the mail settings alone.
Nothing is deleted. Your old hosting account, its files, any mailboxes on it, and its billing all carry on as before.

What happens in the weeks after

The old hosting account now just sits there. It will:

Keep charging you at its next renewal, often yearly. Hosting renewals tend to arrive when nobody is looking, sometimes at a higher price than you signed up for.
Keep any mailboxes running, if your email is provided by that host.
Keep any old files: photos, PDFs, forms, backups.
Keep needing updates, if it is a WordPress site. An abandoned WordPress install with old plugins can still be hacked, even when no customer sees it.

What to check before you cancel anything

Do not cancel the old hosting on launch day. Wait two to four weeks, and in that time work through this list:

Where does your email live? Log in to wherever your domain's DNS settings are and look at the MX records, which say where your mail is delivered. If they mention your old host's name, your mailboxes live there, and cancelling the hosting will delete them. Move email first. Moving your business email to a new provider walks through that.
Is anything still linked to the old files? A PDF menu that a partner site links to, a price list in your email signature, an image used in your Google profile. Copy these to the new site and update the links.
Did you save everything? Text, photos, documents and a full backup from the host's control panel. Once the account is closed, hosts usually delete the files soon after.
Is the domain registered through the old host? If you bought the domain as part of the hosting package, cancelling the hosting can cancel the domain too, or leave it to expire. Move the domain to an account you control first. How to transfer a domain to another registrar explains how.
Are there other services on the account? Some hosting accounts also hold a second website, a shop, or an SSL certificate you paid for separately.

When to cancel what

Cancel the old hosting: two to four weeks after launch, once the new site is working, email is confirmed independent, and everything is saved. If the renewal is months away, you can leave it until then, but turn off auto-renew now so it does not surprise you.

Cancel the old builder subscription: same timing. If your old site was on Wix, Squarespace or GoDaddy's builder, check whether the domain is held by the same company before you cancel. Builders often sell the domain and the site together.

Cancel old add-ons: booking widgets, form services or plugins you no longer use. Look through your card statements for the yearly charges, since these are easy to forget.

Never cancel the domain. Even if you are unhappy with the registrar, move the domain to a new one rather than letting it lapse. An expired domain can be bought by someone else, sometimes within weeks, and getting it back can be impossible. Domain renewal: what happens if your domain expires covers this.

What happens to the old site on Google

Google learns about your new site by visiting your address and finding the new pages. If the new site keeps every old page address, or forwards each old one to its new page, Google follows those and gradually replaces what it shows. Pages that vanish without forwarding turn into error pages for anyone clicking an old result. This is handled on the new site, not the old one, so you can cancel the old hosting without affecting it.

If the old site was on a free or bundled plan

Some old sites came free with an internet package, a phone directory listing, or a hosting account from years ago. These can be hard to cancel because nobody remembers the login. If the domain is pointed away and you are not being billed, there is little harm in leaving it. If you are being billed, call the company with your account number from the statement.

What to do over the next month

Turn off auto-renew on the old hosting now, so it cannot renew without you.
Check where your email lives before touching anything.
Save files and a backup from the old host.
Confirm the domain is in an account you control.
After two to four weeks, cancel the old hosting and any unused add-ons.
Keep the domain renewing every year.

If you are still deciding whether to replace the old site, there is no harm in looking first: you can see your site rebuilt first while the old one keeps running untouched, and only plan the switch once you are happy.