Best Way to Upgrade Shopify Legacy Customer Accounts

Upgrading from legacy customer accounts is a switch in your admin, and you can reverse it for 30 days. That makes it sound trivial, and for a lot of stores it genuinely is. The reason it goes wrong is not the switch. It is that customer accounts sign people in with a code sent by email, so if one email setting is not right, every customer is locked out at once and your storefront looks fine the whole time.

What the upgrade actually does

Legacy customer accounts use email and password, with Liquid templates in your theme that you can edit. Customer accounts are passwordless. The customer enters an email address, receives a one-time six digit code, and signs in. There is no password.

Your customer records are not replaced. The same customers, orders and addresses carry through. What changes is how they prove who they are, and where the account pages live.

Shopify also handles the links. Its upgrade documentation states that "Shopify automatically redirects all legacy customer account URLs," so old links in emails and bookmarks do not break.

You have 30 days to change your mind

This is the part that should lower your anxiety about the whole thing. Shopify's documentation is explicit: "You can revert within 30 days."

So the upgrade is not a one-way door for the first month. That changes the sensible approach. Rather than planning for a quarter, most stores are better off doing the pre-flight checks below, upgrading, and watching the first week closely with the revert option in their back pocket.

After 30 days it is permanent, so use the window rather than assuming it will still be there.

The email setting that locks everyone out

Buried in Shopify's pre-upgrade checklist is an item that carries more weight than its placement suggests: confirm your sender email address is current and accessible.

Think about why. With passwordless sign-in, the login code arrives by email from your store's sender address. If that address is misconfigured, unverified, or pointing at a mailbox nobody owns any more, the codes do not arrive. Every customer trying to sign in simply fails, and there is no error on your storefront to tell you. Your store looks completely healthy while nobody can get into their account.

With the old system a broken sender address meant password reset emails failed, which was annoying. With the new one it means authentication itself fails. Check this before you flip the switch, and test it by requesting a code yourself.

What stops working

Four things, taken from Shopify's own upgrade guidance rather than from guesswork.

Your customers Liquid templates. Customisations in the customers templates folder no longer apply. Anything you built there, extra fields, loyalty widgets, custom links, needs rebuilding as customer account UI extensions or replacing with an app.

Workflow automations built on legacy accounts. Shopify states that "Workflow triggers or automations based on legacy customer accounts aren't supported in customer accounts," and that existing ones cannot be migrated. If your Flow automations fire on legacy account events, they need rebuilding.

Customer segments using account status. Segments that include the customer_account_status filter "won't work as expected." If you send marketing to a segment defined that way, check it before and after.

Multipass. Shopify is direct that "Multipass isn't supported on customer accounts." If you use Multipass to sign customers in from an external site, that flow ends at the upgrade, and it needs a different approach. We covered what replaces it in our piece on customer accounts and where Auth0 fits.

Custom sign-in experiences need clearing first

One item worth calling out separately because it catches stores that consider themselves simple. If somebody built a custom sign-in or registration experience in a modal, or on a page separate from the legacy account templates, you may need to edit your theme to remove those customisations before upgrading.

This is common. A login modal in the header, a registration form embedded on a landing page, a newsletter signup that also creates an account. None of those live in the customers templates folder, so a quick look at that folder will not reveal them. Search your theme for account and login URLs rather than trusting the folder.

The pre-flight checklist

Shopify's own list, in the order we would run it.

• Confirm the sender email address is current and someone can access it. Then request a login code and confirm it arrives.
• Review every customisation in the customers templates folder. Write down what each one does for the business, not what it is called.
• Search the wider theme for custom login or registration entry points. Modals, landing pages, embedded forms.
• Check your Flow automations for anything triggered by legacy account events.
• Check your customer segments for the account status filter.
• Identify replacement apps for anything you are losing, and install them before rather than after.
• Verify brand settings so the hosted account pages look like your store.
• Test every sign-in option before upgrading.

For a store with a standard theme and no custom account work, that is an afternoon. For a store with a loyalty programme, a membership tier and a custom login modal, it is a project, and the useful output of the checklist is finding out which one you are.

What to tell your customers

Mostly nothing, but there is one exception worth handling.

Customers who had a password are about to stop being asked for one. That is a better experience, but it is unfamiliar, and a percentage of people will assume something is wrong when a site stops asking for a password. A short line in your next email, explaining that signing in now uses a code sent to their inbox, prevents a support queue.

What you should not do is send a password reset style announcement. There are no passwords to reset, and framing it that way creates exactly the confusion you are trying to avoid.

Do customers need to reset their passwords?

No. Customer accounts are passwordless, so there is nothing to reset. Customers sign in with a one-time six digit code sent to their email address. This removes password reset tickets entirely, but it is a visible change in experience, so tell people before rather than after.

Can I undo the upgrade if it goes wrong?

Yes, within 30 days. Shopify's documentation states you can revert inside that window, after which the change is permanent. Treat those 30 days as the real testing period and watch sign-in behaviour closely during the first week.

Will I lose customer data when I upgrade?

No. Customer records, order history and addresses carry through. What changes is the authentication method and the account page experience, not the underlying data. Shopify also redirects legacy customer account URLs automatically, so existing links keep working.

Does Multipass still work after upgrading?

No. Shopify states that Multipass is not supported on customer accounts. If you rely on Multipass to sign customers in from an external site, resolve that before upgrading rather than discovering it afterwards, because it is the one item on this list with no simple replacement.

What happens to my loyalty or membership app?

It depends whether the app uses customer account UI extensions or the legacy Liquid templates. Apps built on legacy templates will not display on customer accounts. Check with each app vendor before upgrading, and install the compatible version in advance so there is no gap.

Should I upgrade now or wait for the deadline?

Now, for most stores. Legacy customer accounts were deprecated on 26 February 2026 and Shopify has said a final sunset date will be announced later in 2026, which means the date is not published yet. Upgrading while you have a 30 day revert window and no time pressure is a considerably better position than upgrading against an announced deadline alongside everyone else.

Get your upgrade checked before you flip the switch

Free pre-upgrade check. Email hello@exactwhy.com with subject "Customer accounts" and your store URL. We look at what your customers templates folder actually contains, whether you have custom login entry points elsewhere in the theme, and whether anything depends on Multipass. We respond within 4 hours. For plenty of stores the answer is that you can do this yourself this week, and we will say so.

Prefer a form? Send it through the contact page instead. It reaches the same inbox and you can attach whatever is useful.

Paid upgrade, Rs 40,000 to Rs 1.5 lakh. We audit the customisations, rebuild what matters as customer account UI extensions, replace lost automations, test every sign-in path including the email delivery, and stay close through the revert window.

Ongoing Shopify development, Rs 20,000 to Rs 50,000 a month. Including watching for the sunset date announcement, which has not been made yet.

If you take one thing from this, make it the email check. Every other item on the list produces a visible problem you can fix. A broken sender address produces a store that looks perfectly fine to you and locks out every customer who tries to sign in. Our wider notes on scoping custom Shopify work cover how we price the rest of it.