Beyond Login: What You Can Build with Passwordless OTP Authentication

Passwordless authentication is often treated as a UX upgrade—fewer passwords, fewer resets, happier users. But when implemented correctly, OTP-based authentication (via SMS, WhatsApp, or email) becomes something much bigger: a product primitive you can build entire applications around.

Using modern auth platforms like Supabase Auth combined with Twilio Verify, developers can shift identity away from passwords entirely and toward real-world ownership—a phone number, a WhatsApp account, or an inbox.

This article explores what becomes possible once authentication is no longer a barrier, but a feature.

The Core Idea: Identity Without Passwords

Traditional auth assumes users want long-lived credentials. In reality, users want access, not accounts.

Passwordless OTP flips the model:

  • Identity is verified just in time

  • Credentials expire naturally

  • Users authenticate using something they already have

  • Risk is reduced via rate limits, fraud detection, and short-lived sessions

With Supabase handling sessions and Twilio Verify handling OTP delivery, the developer focuses on flows, not cryptography.

What This Unlocks

1. Frictionless Consumer Apps

Mobile-first apps benefit immediately:

  • Fitness trackers

  • Journaling apps

  • Expense splitters

  • Habit builders

Users can install, authenticate, and onboard in seconds—especially on iOS where OTP autofill removes manual input entirely.

Result: Higher conversion, lower abandonment, fewer support tickets.

2. Communities with Built-In Trust

Phone-based identity dramatically reduces spam and sock-puppet accounts.

Ideal for:

  • Local neighborhood platforms

  • Campus or alumni communities

  • Dating or discovery apps

  • Event-based social networks

A phone number becomes a lightweight trust signal without requiring government ID or invasive KYC.

3. WhatsApp-Native Products

When WhatsApp is both the login channel and communication channel, new product categories emerge:

  • Customer support portals

  • Order tracking dashboards

  • Appointment booking systems

  • Logistics notifications

Users authenticate via WhatsApp and continue interacting in the same channel—no context switching.

4. Internal Tools & Workforce Apps

Passwordless OTP is especially powerful for non-desk workers:

  • Delivery drivers

  • Warehouse staff

  • Field technicians

  • Temporary contractors

No passwords to forget. No credential sharing. Access can be revoked instantly by disabling a phone number.

5. Lightweight Fintech & Wallets

For low-to-medium risk financial products, OTP-based auth is often sufficient:

  • Expense sharing

  • Loyalty wallets

  • Micro-savings apps

  • Subscription management

Security comes from short-lived sessions and transaction-level verification rather than static passwords.

6. Healthcare & Civic Portals (Tiered Access)

Not all healthcare or government interactions require full identity verification.

OTP works well for:

  • Appointment scheduling

  • Viewing test results

  • Submitting service requests

  • Status tracking portals

Sensitive actions can still be gated behind additional verification when needed.

7. Education & Knowledge Platforms

OTP removes friction for large, rotating user bases:

  • Online courses

  • Corporate training

  • Exam registration

  • Internal documentation portals

Users don’t need to remember accounts—they just need access when it matters.

8. Temporary & Event-Based Products

Because OTP identity is ephemeral, it’s perfect for:

  • Conferences

  • Pop-up events

  • Ticketed experiences

  • Time-limited SaaS trials

Access can exist for minutes, hours, or days—then disappear without cleanup.

Step-by-step GUIDE

This guide walks alongside the video and gives you click-by-click setup, plus terminal commands, and copy/paste prompts you can use to keep yourself on track.

What you’ll build

A passwordless login flow where users:

  1. enter a phone number

  2. tap Send OTP (SMS by default)

  3. enter the OTP

  4. get signed in (Supabase session)

  5. optionally switch the OTP channel to WhatsApp

You’ll also see how to do Email OTP by tweaking the Magic Link template.

Prerequisites

  • A Supabase project (with Auth enabled)

  • A Twilio account with access to Twilio Verify

  • Node.js + npm installed

  • Expo CLI / Expo Go installed

Prompts (copy/paste checklist)

  • “Do I have access to Twilio Verify in my Twilio account?”

  • “Do I have a Supabase project created, and can I access Auth settings?”

  • “Am I using Expo (React Native) and can I run expo start successfully?”

1) Create a Twilio Verify Service (Console)

  1. Open the Twilio Console.

  2. Go to Verify.

  3. Create a new Verification Service.

  4. Give it a name (example from the video: super passwordless login).

  5. Enable channels:

    • ✅ SMS

    • ✅ WhatsApp

  6. Turn on Fraud Guard (recommended in the video to help protect from SMS dumping fraud).

✅ Copy your Verify Service SID (you’ll paste this into Supabase next).

Prompt

  • “Did I enable Fraud Guard and copy the Verify Service SID?”

2) Get Twilio credentials (Account SID + Auth Token)

In Twilio Console:

  1. Go to API Keys & Tokens (or the equivalent account credentials page).

  2. Copy:

    • Account SID

    • Auth Token (use the appropriate environment, e.g., live credentials if that’s what you’re testing with)

Prompt

  • “Do I have the Account SID, Auth Token, and Verify Service SID ready to paste?”

3) Configure Supabase Auth to use Twilio Verify for Phone OTP

In Supabase Dashboard:

  1. Go to Authentication → Providers

  2. Find Phone and enable it

  3. For the provider type, select Twilio Verify (important: this is different from the basic Twilio SMS API integration)

  4. Paste:

    • Twilio Verify Service SID

    • Twilio Account SID

    • Twilio Auth Token

  5. Save changes

Prompt

  • “In Supabase, did I select Twilio Verify (not Twilio SMS) and save successfully?”

4) Run the Expo starter project (Terminal)

The video uses an Expo user management starter. If you already have a Supabase Expo starter, use yours.

Terminal commands (typical Expo flow)

# install dependencies
npm install

# start expo
npx expo start

If you need to clear cached bundler issues:

npx expo start -c

Prompt

  • “Can I open the app in Expo Go (or simulator) and see the starter running?”

5) Update the Auth UI: swap Email → Phone + OTP

In your Auth component (the video mentions an Auth component), make these UI updates:

UI changes

  • Rename the “email” input to phone

  • Keep the “password” field but treat it as OTP

  • Update button labels:

    • “Sign in” → Send OTP

    • “Sign up / Verify” → Verify OTP

Prompt

  • “Does my UI now have: phone input + OTP input + Send OTP + Verify OTP?”

6) Implement “Send OTP” with Supabase Phone OTP

When the user taps Send OTP, call Supabase to trigger an OTP to that phone number.

Implementation intent

  • Take the user’s phone string (include country code)

  • Call the phone OTP method (the video logs data to see what comes back)

  • Confirm you see a response without errors

Prompt

  • “When I tap Send OTP, do I see a successful response and receive an OTP message?”

7) Implement “Verify OTP” to create a session

When the user enters the OTP and taps Verify OTP:

  • Pass:

    • phone

    • token (the OTP code)

    • type: "sms" (or equivalent)

Successful verification should return a session and sign the user in.

Prompt

  • “After Verify OTP, do I see a session and does my app show the user as logged in?”

8) Improve UX: enable iOS OTP autofill

The video calls out a key UX improvement:

  • The OTP input should NOT be secureTextEntry

  • When it’s not secure entry, iOS can offer OTP autofill directly from the SMS

Checklist

  • OTP input is plain text (not password-masked)

  • Test on iOS device if possible

Prompt

  • “On iOS, does the OTP suggestion appear above the keyboard after the SMS arrives?”

9) Switch OTP channel to WhatsApp

To use WhatsApp OTP, you add a channel option and set it to WhatsApp before sending the OTP.

Flow

  1. User taps “Send OTP”

  2. OTP is delivered via WhatsApp instead of SMS

  3. User enters OTP

  4. Verify OTP normally

Note from the video

  • WhatsApp may not support the same iOS OTP autofill behavior as SMS.

Prompt

  • “Did the OTP arrive in WhatsApp, and can I verify it to get a session?”

10) Optional: Email OTP (using Magic Link template)

The video mentions you can do OTP with email too:

  1. In Supabase Auth settings, go to Email templates

  2. Edit the Magic Link template:

    • Replace the confirmation URL approach

    • Include a token in the email body instead

  3. Then verify that token using the same OTP verification flow conceptually

Prompt

  • “Can I receive an email that contains a token (OTP) and verify it to obtain a session?”

Troubleshooting checklist

OTP never arrives

  • Confirm phone number format includes country code

  • Confirm Verify Service is enabled for SMS/WhatsApp

  • Check Twilio logs / Verify logs

Costs / fraud

  • The video warns SMS can be expensive and mentions SMS dumping fraud

  • Use Verify + Fraud Guard + rate limits

“Verify succeeds but I’m not logged in”

  • Confirm you are storing/using the returned Supabase session properly

  • Confirm the client is configured with your Supabase URL + anon key

Quick “follow-along” prompts (copy/paste)

  • “I created a Twilio Verify Service with SMS + WhatsApp and enabled Fraud Guard.”

  • “I copied my Verify Service SID, Account SID, and Auth Token.”

  • “In Supabase Auth → Phone, I selected Twilio Verify and pasted credentials.”

  • “My Expo app runs locally via npx expo start.”

  • “My UI has Phone + OTP + Send OTP + Verify OTP.”

  • “Send OTP triggers a message and Verify OTP returns a session.”

  • “OTP input is not secureTextEntry so iOS autofill works.”

  • “Switch channel to WhatsApp and confirm OTP arrives there.”

If you tell me what stack you’re using (Expo + TS? Next.js? Flutter?), I can tailor the exact code snippets and the exact Supabase method names to match your project so you can literally copy/paste end-to-end.

Why This Architecture Works

The strength of this methodology lies in delegation:

  • Twilio Verify handles delivery, rate limiting, and fraud protection

  • Supabase manages sessions, persistence, and user records

  • Your app defines the product logic

Authentication becomes invisible infrastructure, not a product bottleneck.

A Shift in How We Design Products

Passwordless OTP isn’t just about removing passwords—it’s about removing assumptions.

  • Users don’t want long-term credentials

  • Identity doesn’t have to be permanent

  • Security can be contextual, not static

Once you internalize this, you stop asking “How do users sign up?”
and start asking “What should access look like?”

That’s where new products emerge.

If you’d like, this article can be adapted into a technical deep dive, architecture diagram walkthrough, or a region-specific guide (SMS vs WhatsApp vs Email). Just say the word.

Vibe Coding, SupabaseFrancesca Tabor