Website address with or without www: does it matter?

It does not matter whether your website lives at www.yourbusiness.com or plain yourbusiness.com. Google treats both the same, and customers reach you either way. What does matter is that you pick one as the main address, make the other one forward to it automatically, and use the main one everywhere you list your site. Getting that wrong is what causes trouble, not the choice itself.

Why there are two addresses at all

Technically, yourbusiness.com and www.yourbusiness.com are two different addresses. The "www" part is what is called a subdomain, a name in front of your domain, like shop. or mail.. Decades ago it was the convention to put websites on the www subdomain, and it stuck.

Because they are two addresses, each one has to be set up to work. If only one is set up, customers who type the other get an error. If both are set up but show the site separately, Google sees two copies of every page.

What can go wrong

These are the problems that come from not choosing, and you can check for each of them in a minute.

One version does not open. A customer types www. out of habit and gets "This site can't be reached". This is common after a website move when only one version was pointed at the new site.
Both versions open, with no forwarding. The site loads at both addresses, and the address bar keeps whatever the visitor typed. Google may split its attention between the two copies, and links to your site get split too.
The padlock only works on one. The security certificate, the thing that makes the padlock appear, covers one version but not the other. Visitors on the uncovered one see a warning.
Your listings disagree. Your Google profile says www, your Facebook page says without, your business cards say a third thing. Each works if forwarding is set up, but mixed addresses make the setup harder to keep right.

How to check your own site

Do this on your phone and on a computer.

Type yourbusiness.com into the address bar and press enter. Note what is in the address bar after the page loads.
Type www.yourbusiness.com. Note what is in the address bar.
Try http://yourbusiness.com and http://www.yourbusiness.com too, typing the http:// part yourself.

All four should end up on the same address, with the padlock showing. If they do, you are done. If any of them shows an error, a warning, or stays on its own version, the forwarding needs fixing.

Which one to choose

If your site already uses one version and it works, keep it. Switching costs a little effort and gains nothing.

If you are setting up a new site, either is fine. Some practical points:

Without www is shorter to say and to print. Many newer sites use it.
With www is what many older customers still type by habit, though forwarding takes care of that.
Some setups make one easier. With some domain companies, pointing the bare domain at a website is less flexible than pointing the www version, because of how the records for a bare domain work. Whoever sets up the site will know which one fits.

Whatever you choose, it does not change how Google sees your business.

How the forwarding should work

The forwarding from the version you do not use to the one you do should be a permanent redirect, called a 301. It tells browsers and Google "this address has moved here for good". It should also keep the rest of the address: www.yourbusiness.com/services should go to yourbusiness.com/services, not to your home page.

Where to set it depends on your setup:

Website builders usually handle it automatically once you connect your domain. In the domain settings, look for which version is marked as the main or primary one.
WordPress has two address fields under Settings, then General. Both should use your chosen version. The host or a plugin handles the forwarding.
Your domain company can sometimes forward one version to the other in its DNS settings, the part of your domain account that says where your site and email live. DNS explained for small business owners explains those settings without jargon.

Telling Google which one you use

Google figures it out from the forwarding, so there is little extra to do. Two things help:

In Search Console, add your site as a Domain property. That covers both versions, with and without www, and http and https, in one report.
Make sure your sitemap and the internal links on your site all use the main version.

Using it everywhere

Once you have chosen, write it the same way wherever you list your website: your Google Business Profile, Apple and Bing listings, Facebook, Yelp, email signature, invoices, van lettering and business cards. On printed material you can drop the https:// and even the www., since forwarding catches it, but keep your online listings exact.

If you move to a new website later, the forwarding has to be set up again for both versions. That is part of a wider checklist covered in connecting your domain to a new website.

What to do this week

Type all four versions of your address and see where each one ends up.
Check the padlock appears on every version.
Note which version your site uses and check your Google profile matches.
If one version fails, ask your web person or builder support to set a permanent redirect to the main one.
Add your site to Search Console as a Domain property.

If your current site is the kind where a simple fix like this means calling someone and waiting, you can see your site rebuilt first, with both versions of the address handled when it goes live.