Blog
Phone verification, two-factor authentication and messaging that reaches people, written for the developers and teams who build it.
- The top 5 SMS verification providers, and when to send the code on WhatsApp insteadTwilio Verify, Vonage Verify, Prelude, Plivo Verify and Sinch Verification compared by channels, fraud protection and fallback, plus when a WhatsApp code is the better choice.
- How to choose an SMS service for two-factor authenticationA practical checklist for picking an SMS or OTP provider for 2FA, covering delivery in your countries, pricing model, SMS pumping protection, fallback, sender registration and autofill.
- Verification APIs compared for developersHow the major OTP and verification APIs work from a developer's side, from the start-and-check flow to fallback, idempotency, rate limits and testing, and how to keep your code provider independent.
- SMS vs authenticator apps vs WhatsApp codes for two-factor authenticationThe pros and cons of SMS two-factor authentication compared with authenticator apps, passkeys, email and WhatsApp codes, what NIST says about SMS, and which factors to offer your users.
- OTP code not arriving? A troubleshooting guide for SMS and WhatsApp verificationWhy verification codes fail to arrive or fail to verify, and how to fix it, from number formatting and carrier filtering to rate limits, autofill, WhatsApp delivery and SMS pumping.
- Twilio vs Oxtro: which fits your WhatsApp messaging?An honest comparison of Twilio and Oxtro for WhatsApp messaging and OTP, covering the official API versus your own number, setup, templates, pricing model, team inbox, API and risk.
- SMS vs WhatsApp for business messages: which should you use?When to message customers by SMS and when on WhatsApp, compared on reach by country, two-way conversation, media, delivery receipts, cost model, rules and risk, and how to use both.
- WhatsApp automation on Android: tools, limits and strategiesWhat you can automate in WhatsApp from an Android phone with the Business app, where auto-reply apps fall short, and how to move to a shared inbox and API without losing your number.
- 5 message patterns that get SMS and WhatsApp messages flagged as spamThe spam trigger words, promotional tone, caps and emojis, links and missing opt-outs that get business SMS filtered and WhatsApp numbers restricted, and the habits that keep messages delivered.
- Build your own Android SMS gateway in 10 stepsHow to turn an Android phone into an SMS gateway with a REST API, from choosing a SIM and open-source app to webhooks, delivery reports, Android's sending limit and keeping it running.
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