Customer authentication plays a central role in the overall user experience of any e-commerce store. Traditional email-and-password login systems often introduce friction, especially in markets where mobile usage dominates and customers prefer faster, simplified authentication methods. Phone number-based login with One-Time Password (OTP) verification provides a streamlined alternative that reduces barriers to entry while improving conversion rates. In Shopify, customer accounts are traditionally based on email and password authentication. However, many modern stores require phone-first login systems, particularly in regions where SMS-based authentication is standard practice. While building a custom OTP system from scratch requires backend infrastructure, API integrations, SMS gateway management, and secure token validation, Shopify’s app ecosystem enables merchants to implement OTP login without writing backend code. This documentation provides a complete, structured guide for implementing phone number (OTP) login on any Shopify store using a free plan available on the Shopify App Store. The guide is written for developers, technical Shopify users, and non-technical store owners. It explains not only how to install and configure the solution but also how Shopify themes, app embeds, and customer account systems interact during implementation. The goal is to provide a professional, implementation-focused walkthrough suitable for official documentation and long-term reference.

OTP login allows customers to authenticate using their phone number. Instead of creating a password, customers receive a time-sensitive code via SMS, which they enter to gain access.

Conceptually, the process works as follows:

• The customer enters their phone number.

• The system generates a secure OTP.

• The OTP is sent through an SMS gateway.

• The customer enters the OTP.

• The system verifies the code.

• If valid, the customer session is created.

In Shopify, third-party apps handle:

• OTP generation

• SMS dispatch

• Code validation

• Customer record linking

• Session creation

Shopify itself does not natively generate SMS-based OTP for login without external integration.

It is important to distinguish between frontend and backend roles.

The frontend is responsible for:

• Displaying the phone number input field

• Displaying the OTP field

• Handling user interaction

• Sending requests to the app server

The backend (managed by the OTP app) is responsible for:

• Generating secure OTP tokens

• Managing SMS provider integration

• Validating OTP submissions

• Linking phone numbers to Shopify customer accounts

• Creating authenticated sessions

Because the app manages backend logic externally, no custom server development is required by the merchant.

Before installation, ensure the following:

1. You have administrative access to your Shopify store.

2. You are using Classic Customer Accounts.

3. Your theme supports app embeds.

4. Your store has a configured customer login page.

If your store uses New Customer Accounts, OTP apps may not inject properly into the login template. Switching to Classic Customer Accounts may be necessary.

To install the required application, follow these steps:

1. Open your Shopify Admin panel.

2. Navigate to Apps.

3. Click Shopify App Store.

4. In the search bar, type “OTP login.”

5. Locate the app named “Simply OTP Login.”

6. Open the app listing page.

7. Click Install.

8. Approve the required permissions.

9. Complete the installation process.

Once installed, the app will appear in your Shopify Admin under Apps.

After installation, the app may display an introduction or onboarding tour.

Follow these steps:

1. Open the app from your Shopify Admin.

2. If an introduction tour appears, you may review it or skip it.

3. Navigate to the Dashboard.

4. Open the Plans section.

5. Review available subscription plans.

6. Select the Free Plan.

7. Confirm subscription.

Even free plans require activation. Ensure that the plan status shows as active before proceeding.

The free plan typically includes limited OTP usage per month. Review usage limitations carefully.

Most modern Shopify apps inject functionality using App Embeds.

Follow these steps to enable it:

1. Go to Online Store.

2. Click Themes.

3. Click Customize on your active theme.

4. Open Theme Settings.

5. Scroll to the App Embeds section.

6. Locate “Simply OTP Login.”

7. Enable the toggle switch.

8. Click Save.

Enabling the app embed allows the application to inject scripts and styles into your theme globally. Without enabling this step, the OTP widget will not function correctly.

App embeds are responsible for:

• Injecting JavaScript for OTP handling

• Connecting frontend input fields to backend validation

• Rendering dynamic login components

OTP login apps typically integrate with Classic Customer Accounts.

Follow these steps:

1. Go to Shopify Admin.

2. Navigate to Settings.

3. Click Customer Accounts.

4. Ensure Classic Customer Accounts is selected.

5. Save changes.

If your store is using New Customer Accounts, the login page customization options may not allow OTP widget insertion.

After enabling app embed and activating Classic Customer Accounts, you must insert the OTP widget into the login page template.

Follow these steps:

1. Go to Online Store.

2. Click Customize.

3. Use the page selector dropdown at the top.

4. Select Customer Login.

5. Click Add Section.

6. Choose Apps.

7. Select the “Simply OTP Login” app block.

8. Position the block appropriately.

9. Click Save.

This step attaches the OTP login widget to your customer login page.

Internally, the app block injects structured markup and script hooks into the page. The app’s backend handles OTP verification when users interact with the widget.

No manual code editing is required in this process.

After saving changes, open your store’s login page.

You should now observe:

• A phone number input field

• An option to request OTP

• An OTP verification field after submission

Test the flow by:

1. Entering a valid phone number.

2. Requesting an OTP.

3. Entering the received code.

4. Confirming login.

If configured correctly, a customer session should be created.

The app either:

• Links the phone number to an existing customer

• Creates a new customer profile automatically

Behavior may depend on app configuration settings.

The app provides customization options within its settings panel.

You can configure:

• Login title text

• Subtitle text

• Widget alignment

• Custom image uploads

• GIF, PNG, JPG support

• Direct image URL embedding

To customize:

1. Open the app dashboard.

2. Navigate to Settings.

3. Locate Widget Customization.

4. Upload images or provide URLs.

5. Modify login title text.

6. Save changes.

The uploaded image may function as:

• A visual banner

• A branding element

• A promotional asset

Customization does not alter backend OTP logic. It only changes frontend appearance.

Even though no code is written manually, it is important to understand the underlying process.

When a customer enters a phone number:

Add your code here

This script captures the input and sends it to the app server via an API request.

The server:

• Validates phone number format

• Generates a secure OTP

• Stores it temporarily with expiration

• Sends the OTP via SMS gateway

When the user enters the OTP:

Add your code here

The app verifies:

• OTP matches stored value

• OTP is not expired

• OTP has not exceeded retry limits

If validation succeeds:

• The app authenticates the customer

• Shopify session is created

• The user is redirected to account page

All backend security logic is managed by the application provider.

While the free plan is functional, several constraints must be considered:

• Monthly OTP limits may apply.

• SMS delivery rates depend on geographic region.

• Some countries may have SMS restrictions.

• Integration may not support New Customer Accounts.

• High traffic stores may require upgraded plans.

Additionally, third-party dependency means:

• Service availability depends on the app provider.

• SMS gateway outages can disrupt login.

• Future Shopify platform changes may affect compatibility.