The point isn’t to blame the user. Ever notice how, when login goes sideways, it’s almost always marketed as "user error"—“You didn’t get the code,” or “You entered it wrong.” But you know what’s funny? The real culprit usually lurks in the way critical one-time password (OTP) messages are delivered, formatted, and handled behind the scenes.
This blog dives into a hotly debated aspect of otp message security: putting your verification code directly in the SMS preview. We’ll explore common reasons OTPs fail to reach or work for users, why blasting more messages on the same channel can backfire, and how a smart multi-channel approach can save the day. Along the way, you’ll find facts backed by authorities like Sent API and security agencies like CISA, and recommendations for improving the best format for OTP SMS that balances security and the user experience (UX).
Why Does OTP Delivery Keep Failing?
Before we unravel if it’s safe to put codes in SMS previews, let’s sketch the usual OTP delivery pain points:
- Carrier filtering: SMS carriers increasingly filter or block messages that look like spam or contain suspicious patterns. Bombarding users with multiple OTPs on the same channel almost guarantees your messages end up in a black hole. Poor formatting: Put a verification code buried in the middle of a wall of text and the user can’t find it quickly. They’ll get frustrated and either abandon the process or ask support for help — increasing operational costs. Device settings and app behavior: Different phone models handle SMS previews inconsistently. Sometimes, notifications don’t show the code prominently, or SMS apps truncate crucial parts. Latency and network issues: SMS isn’t guaranteed instant delivery. Congestion, roaming, or bad signal can delay or drop OTP messages. Security policies: Companies worried about SIM-jacking or phishing might hide OTPs or avoid putting them in clear text, but this can hurt usability.
Ever notice how many companies try to throw more OTP messages at users, thinking more messages equals higher success? No. That’s just spamming the channel, annoying users, and increasing cost with minimal improvement. It’s a common misguided approach, and honestly, it’s a lazy fix.
Is It Safe to Put the Code in the SMS Preview?
Let’s cut through the jargon. The SMS preview is the part of the message users see without opening the SMS app—those pop-up notifications on iOS or Android. Putting the OTP code here makes it easier for users to copy or type the code quickly.
Pros of putting the code in SMS preview:
- Better usability: Users get instant access to codes without tapping into the message, speeding up login or verification. Supports autofill: Phones can read the code from the preview and suggest autofill, cutting errors and support tickets. Reduces confusion: Clear formatting with the code front and center helps users find it fast.
Cons and security considerations:
- Exposure risk: If someone else can see your phone’s locked screen, they may see the OTP and misuse it. SIM swap attacks: SMS, including previews, is vulnerable if attackers take control of the phone number. But this risk is separate from preview visibility and more about the channel itself.
The Cybersecurity and Infrastructure Security Agency (CISA) acknowledges SMS phishing and SIM swap threats but still recognizes SMS as a widely accessible and reliable second factor when combined with proper user education and fallback methods.
Bottom line? Putting the code in the SMS preview is, on balance, a UX win that most companies should adopt—especially when paired with hiding verification codes behind short, well-formatted messages without unnecessary clutter.
Best Practices for OTP Formatting and Auto-Fill
Here’s a straightforward checklist for the best format for OTP SMS—based on research, Sent API guidance, and tested real-world usage:
Keep it short and clear: Start your SMS text with the OTP code. For example, “123456 is your MyApp verification code.” Use standard keywords like “code”: Phones and autofill apps look for predictable patterns to detect OTPs automatically. Limit to one code per SMS: Don’t confuse the user with multiple codes or extraneous links cluttering the preview. Timestamp and validity: Mention code expiration simply, “Valid for 10 minutes,” so users know the time limit. Avoid spammy formatting: Don’t overload the message with caps, special characters, or aggressive sales language to stay clear of carrier filters.This kind of clear formula helps mobile platforms present the OTP code right in their notifications, allowing for fast auto-fill while reducing user frustration.
Multi-Channel Delivery Strategy: SMS, Email, Voice, and App
Relying purely on SMS? That’s a recipe for frustration and abandoned transactions. A multi-channel OTP delivery strategy distributes risk and increases reliability.
- SMS: Quick and easy for most users, but subject to carrier issues and security risks. Email: Great backup channel, less immediate but often more secure. Especially useful if you design verification emails with similar clarity and prominence on OTP codes. Voice calls: Useful for visually impaired users or as a fallback, but usually considered intrusive by many. App-based OTP generators: The gold standard for security, independent from phone carriers, but require users to install and maintain apps.
Companies like Sent API recommend intelligent orchestration that doesn't blast the same channel repeatedly. Instead, a system should detect failed delivery attempts and gracefully retry through alternative channels. This reduces user frustration and lowers abuse flags with carriers.
The Importance of Intelligent Fallback Systems
Why does this keep happening? Because legacy systems often don’t talk to each other. They blast OTPs repeatedly on SMS for every attempt, assuming that flooding equals success. It doesn’t.
Intelligent fallback systems are a necessity for any business that wants to maintain high delivery success rates and reduce operational costs. Here’s what they look like in practice:
Step Action Channel Notes 1 Attempt OTP delivery Primary (usually SMS) Send OTP with clear formatting and code in preview 2 If no delivery or user reports failure Secondary (Email) Send same OTP or request new OTP via email, with similar formatting 3 Still unsuccessful or user preference Tertiary (Voice Call) Automated voice call reading the code aloud 4 Final fallback App Push Notification For users with secure apps installed that support push OTPSystems like Sent API’s platform can automate this switch without manual intervention and track delivery stats that are meaningful—none of the vanity “delivery rate” metrics that hide real failures.
UX and Security: Don’t Let One Kill the Other
Too many security teams panic about "hiding verification codes" as though obfuscation alone prevents fraud. CISA’s guidance is clear: security is a layered approach, and usability in OTP delivery is critical to make that effective.
Here’s the truth: if users can’t find or use OTPs quickly, they will call support, delay adoption, or worse—use less secure fallback methods like password resets.
Autofill-ready, preview-visible codes combined with fallback channels and anti-abuse measures like rate limiting and behavior analysis is the winning formula.
Final Thoughts
Putting the code directly into the SMS preview isn’t just safe—it’s smart. It improves user experience massively and doesn’t significantly increase security risk beyond what’s inherent in SMS verification. Instead of blaming users for “not seeing the code,” companies should optimize otp message security through better formatting, less blasting on a single channel, and embracing intelligent multi-channel fallback approaches.
Don’t let poor design and lazy retry strategies frustrate your users or waste your budget. Take a lesson from Sent API and CISA: clarity, improving OTP delivery through API multi-channel resilience, and smart orchestration beat complicated gimmicks every time.
Now, if only every app would get login flows as right as a good OTP message formatting, I'd spend way less time answering “I didn’t get the code” tickets. But hey, a manager can dream.
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