SMS vs Email OTP: Which Is Better for Your Online Store?

When adding OTP login to your store, one of the first decisions is: should customers receive their one-time code via SMS or email?

Both work. Both are secure. But they have different strengths depending on your market, your customers, and your budget. Here's the breakdown.

Speed & Delivery

SMS OTP

• Delivery time: 2-5 seconds (near-instant)
• Deliverability: 95-99% — SMS almost always arrives
• Visibility: Shows as a notification on the lock screen — customers see it immediately without opening an app
• Auto-fill: Modern phones detect OTP codes in SMS and offer one-tap auto-fill

Email OTP

• Delivery time: 5-30 seconds (usually fast, but can be delayed)
• Deliverability: 85-95% — emails can land in spam, promotions tabs, or get delayed by provider queues
• Visibility: Requires opening the email app, finding the message, and copying the code
• Auto-fill: Not supported on most devices

Winner: SMS. Faster, more reliable, and the auto-fill feature reduces the login to essentially one tap after entering a phone number.

Cost

SMS OTP

• Cost per message: $0.005-0.05 depending on country and provider
• Israel (local providers): ~₪0.03-0.08 per SMS (~$0.008-0.02)
• International (Twilio): $0.01-0.08 per SMS depending on destination
• Monthly cost (1,000 logins): $5-50

Email OTP

• Cost per email: Effectively free (most email providers include thousands of sends)
• Transactional email services: $0.0001-0.001 per email
• Monthly cost (1,000 logins): $0-1

Winner: Email. Dramatically cheaper. For stores with tight margins or high login volume, email OTP costs practically nothing.

Conversion Rates

This is where it gets interesting. SMS OTP consistently outperforms email OTP for login conversion:

• SMS OTP completion rate: ~90-95% of customers who request a code will complete the login
• Email OTP completion rate: ~75-85% — customers get distracted switching to email, or the code lands in spam

The 10-15% difference matters. If you get 1,000 login attempts per month, SMS gives you ~100 more successful logins than email. Those are real customers who might have abandoned their cart.

Winner: SMS. Higher completion rates because the code appears on-screen automatically.

Security

SMS OTP

• Strengths: Code delivered to a device the customer physically possesses
• Risks: SIM swapping attacks (rare, targeted, mostly affects high-value accounts)
• Suitable for: E-commerce, social apps, most consumer applications

Email OTP

• Strengths: Works on any device with email access, no phone number required
• Risks: Email accounts can be compromised; emails can be intercepted on shared/public devices
• Suitable for: E-commerce, newsletter subscribers, desktop-heavy audiences

Winner: Tie. Both are significantly more secure than passwords. For e-commerce use cases, the theoretical attack vectors for both are negligible compared to the real-world damage from password reuse.

User Experience

Mobile Shoppers (70%+ of traffic)

SMS wins decisively. The customer is already on their phone. The code appears as a notification and auto-fills. The entire login takes 3 seconds without leaving the browser.

Email on mobile means: switch to email app → find the message → memorize the code → switch back to browser → type the code. That's 15-30 seconds of friction.

Desktop Shoppers

Email has an edge. Desktop users likely have email open in another tab. Copy-paste is easy. SMS requires picking up the phone and typing the code manually.

International Customers

Email is more universal. Not all countries have cheap SMS, and some customers are wary of sharing phone numbers. Email works everywhere with no cost to the customer.

Privacy-Conscious Customers

Email preferred. Some customers don't want to share their phone number with a store. Offering email OTP as an alternative respects their preference.

Why Not Both? (The Right Answer)

Here's the thing: you don't have to choose. The best OTP login implementations offer both SMS and email, letting the customer pick their preferred method.

This gives you:

• Maximum conversion — Every customer can use their preferred method
• Cost optimization — Customers who choose email save you SMS costs
• Full coverage — Works for mobile, desktop, international, and privacy-conscious customers
• Fallback — If SMS doesn't arrive (rare), email is always there

Quick Login supports both SMS and email OTP out of the box. You configure both and let your customers choose — getting the best of both worlds.

Our recommendation: Enable both SMS and email OTP. Default to SMS (higher conversion) but always offer email as an alternative.

Quick Summary

• Speed: SMS wins
• Cost: Email wins
• Conversion: SMS wins
• Security: Tie
• Mobile UX: SMS wins
• Desktop UX: Email wins slightly
• Best answer: Offer both