# Blog

> Guides and research on phone-number verification, fraud prevention and deliverability from the MobileValidate team.

Canonical: https://mobilevalidate.com/blog

- [Carrier and line type lookup, explained](https://mobilevalidate.com/blog/carrier-and-line-type-lookup-explained.md) — 2026-09-25 · Guides: What carrier and line type data is, allocated vs current network, how porting changes it, and how to read every field of a carrier lookup answer.
- [How to check if a phone number uses iMessage](https://mobilevalidate.com/blog/check-if-a-number-has-imessage.md) — 2026-09-25 · Guides: What iMessage registration means, blue vs green bubbles, iMessage vs RCS on iPhone, what businesses can and can't send, and a bulk API example.
- [How to check if a phone number is on WhatsApp with an API](https://mobilevalidate.com/blog/check-if-a-number-is-on-whatsapp-api-guide.md) — 2026-09-25 · Developers: How a WhatsApp registration check works, what registered, not registered and unknown mean, and how to call it responsibly from cURL, Node and Python.
- [How to choose a messaging channel by country](https://mobilevalidate.com/blog/choosing-a-messaging-channel-by-country.md) — 2026-09-25 · Deliverability: WhatsApp, Telegram, Viber, LINE, Zalo, RCS or SMS? How to pick a channel per country for messages customers expect, and measure it on your own base.
- [E.164 phone number format: a practical guide for developers](https://mobilevalidate.com/blog/e164-phone-number-format-guide-for-developers.md) — 2026-09-25 · Developers: How to normalize phone numbers to E.164 in JavaScript and Python, the pitfalls that break deduplication, and how the MobileValidate API normalizes input.
- [E.164 regex: why a pattern is not enough to validate phone numbers](https://mobilevalidate.com/blog/e164-regex-is-not-enough.md) — 2026-09-25 · Developers: The common E.164 regex accepts impossible numbers. Real counterexamples, the shortest valid international numbers, and what to use a regex for instead.
- [E-mail verification vs account existence checks: what's the difference?](https://mobilevalidate.com/blog/email-verification-vs-account-existence-checks.md) — 2026-09-25 · Guides: Mailbox validation says an address can receive mail. An account check says it is registered on a service. When to use each, and the privacy rules.
- [HLR lookup vs MNP lookup vs number validation: what each one answers](https://mobilevalidate.com/blog/hlr-vs-mnp-vs-number-validation.md) — 2026-09-25 · Guides: Validation checks the digits, MNP finds the current network, HLR asks the network if the number is live. What each answers, costs and misses.
- [How to check if a phone number is active (and what "active" really means)](https://mobilevalidate.com/blog/how-to-check-if-a-phone-number-is-active.md) — 2026-09-25 · Guides: Valid, active, reachable and registered mean different things. The methods for checking each one, what they cost and where every method falls short.
- [How to clean a phone number list in bulk, step by step](https://mobilevalidate.com/blog/how-to-clean-a-phone-number-list-in-bulk.md) — 2026-09-25 · Deliverability: A step-by-step way to clean a phone list with the MobileValidate jobs API: free estimate, dedupe, invalid rows, capped cost, CSV download and data purge.
- [How to reduce fake sign-ups with layered phone and e-mail checks](https://mobilevalidate.com/blog/how-to-reduce-fake-signups-with-phone-and-email-checks.md) — 2026-09-25 · Fraud prevention: A layered sign-up defence: format, line type, messaging presence, spam reputation and e-mail checks, mapped to friction tiers you can measure.
- [IRSF: international revenue share fraud, explained](https://mobilevalidate.com/blog/irsf-international-revenue-share-fraud.md) — 2026-09-25 · Fraud prevention: How international revenue share fraud turns your calls and texts into someone else's income, how it differs from SMS pumping, and how to cap your exposure.
- [Is a phone number personal data under the GDPR?](https://mobilevalidate.com/blog/is-a-phone-number-personal-data-gdpr.md) — 2026-09-25 · Guides: When a phone number is personal data under the GDPR, what changes for business numbers, and how lookups and enrichment fit lawful basis, notice and rights.
- [Messaging-app registration checks: a guide for every app](https://mobilevalidate.com/blog/messaging-app-registration-checks-guide.md) — 2026-09-25 · Guides: What a registration check tells you for WhatsApp, Telegram, Viber, Signal, iMessage, RCS, LINE, Zalo and more: modes, unknowns, billing and consent.
- [Mobile number portability: why carrier lookups can be wrong](https://mobilevalidate.com/blog/mobile-number-portability-why-carrier-lookups-can-be-wrong.md) — 2026-09-25 · Guides: A number's prefix shows the network its range was given to, not the one serving it today. How porting works, where lookups fail and how to handle it.
- [How often do phone numbering plans change? 2019–2026 data](https://mobilevalidate.com/blog/numbering-plans-change-research-2026.md) — 2026-09-25 · Research: We counted 182 phone-metadata releases from 2019 to 2026: a median of 14 days apart, and 230 of 245 regions changed. Why validation goes stale.
- [OTP fraud prevention: the checks to run before you send a code](https://mobilevalidate.com/blog/otp-fraud-prevention-checks-before-sending-a-code.md) — 2026-09-25 · Fraud prevention: A practical pre-send pipeline for one-time passcodes: normalize, check line type, messenger presence and reputation in one request, then decide.
- [Phone intelligence for AI agents with MCP](https://mobilevalidate.com/blog/phone-intelligence-for-ai-agents-with-mcp.md) — 2026-09-25 · Developers: How to give an AI agent phone and e-mail checks through the MobileValidate MCP server: tools, example prompts, real tool calls and spend safeguards.
- [How to evaluate a phone number validation API: a buyer's checklist](https://mobilevalidate.com/blog/phone-number-validation-api-buyers-guide.md) — 2026-09-25 · Guides: The criteria that matter when you choose a phone-intelligence API: coverage, conclusive rates, unknown billing, latency, freshness, privacy and test mode.
- [Phone number validation in JavaScript and Node.js](https://mobilevalidate.com/blog/phone-number-validation-javascript.md) — 2026-09-25 · Developers: Validate phone numbers in JavaScript with libphonenumber-js: min vs max metadata, E.164, form input, and a live line-type check with runnable Node code.
- [Phone number validation in PHP and Laravel](https://mobilevalidate.com/blog/phone-number-validation-php-laravel.md) — 2026-09-25 · Developers: Validate phone numbers in PHP with libphonenumber-for-php, write a Laravel rule, and add a live line-type check with Guzzle that never breaks the form.
- [Phone number validation in Python: phonenumbers, Pydantic and a live check](https://mobilevalidate.com/blog/phone-number-validation-python.md) — 2026-09-25 · Developers: Validate phone numbers in Python with the phonenumbers library: is_valid vs is_possible, E.164, a Pydantic validator, pytest and a live check with httpx.
- [A privacy checklist for phone and e-mail checks](https://mobilevalidate.com/blog/privacy-checklist-for-phone-and-email-checks.md) — 2026-09-25 · Guides: A practical GDPR-oriented checklist for phone and e-mail checks: purpose, lawful basis, minimisation, retention, objections, rights, DPAs and logging.
- [RCS capability check: what it tells senders before they send](https://mobilevalidate.com/blog/rcs-capability-check-explained.md) — 2026-09-25 · Deliverability: What an RCS capability check tells you before sending, iPhone support, RCS vs SMS fallback, what RBM is, and a decision table with bulk API examples.
- [The Reassigned Numbers Database (RND), explained](https://mobilevalidate.com/blog/reassigned-numbers-database-explained.md) — 2026-09-25 · Guides: What the FCC Reassigned Numbers Database does, how its yes/no/no-data answers and TCPA safe harbor work, what it costs, and where other checks fit.
- [Screening inbound calls with spam reputation](https://mobilevalidate.com/blog/screening-inbound-calls-with-spam-reputation.md) — 2026-09-25 · Fraud prevention: A call-center workflow for routing inbound calls by spam reputation: levels, reasons, STIR/SHAKEN, limits of the data, and why no_reports isn't safe.
- [SIM swap fraud: the signals to check before you trust an SMS code](https://mobilevalidate.com/blog/sim-swap-fraud-signals.md) — 2026-09-25 · Fraud prevention: What a SIM swap is, which SIM-swap data exists and who can get it, and which signals to combine before you trust an SMS code when that data is missing.
- [SMS delivery receipts vs HLR lookup: before or after you send](https://mobilevalidate.com/blog/sms-delivery-receipt-vs-hlr-lookup.md) — 2026-09-25 · Deliverability: A delivery receipt reports what happened after you sent an SMS. An HLR lookup asks the network before you send. What each can see, miss and cost.
- [SMS pumping: how it works and how to stop it](https://mobilevalidate.com/blog/sms-pumping-how-it-works-and-how-to-stop-it.md) — 2026-09-25 · Fraud prevention: How SMS pumping (artificially inflated traffic) drains OTP budgets, the signals that give it away, and a layered checklist to stop it before you pay.
- [Telegram number check: a practical guide to what it can and can't tell you](https://mobilevalidate.com/blog/telegram-number-check-guide.md) — 2026-09-25 · Guides: How Telegram's phone and username model differs, what a registration check can and can't tell you, how privacy settings affect it, with API examples.
- [US nuisance-call complaints in 2026: what the public data shows](https://mobilevalidate.com/blog/us-nuisance-call-complaints-what-the-data-shows.md) — 2026-09-25 · Research: Our analysis of 362,116 FTC Do Not Call complaints and FCC unwanted-call data: top subjects, robocall share, weekday pattern and trend.
- [VoIP number detection for sign-ups: what works and what to watch out for](https://mobilevalidate.com/blog/voip-number-detection-for-signups.md) — 2026-09-25 · Fraud prevention: Why VoIP numbers matter at sign-up, fixed vs non-fixed VoIP, which signals detect them, and how to add friction without turning away real customers.
- [WhatsApp Business account check: what the business flag tells you (and what it doesn't)](https://mobilevalidate.com/blog/whatsapp-business-account-check-what-it-tells-you.md) — 2026-09-25 · Guides: What the WhatsApp Business flag means, how it differs from a personal account, its limits, and how B2B and support teams can use it responsibly.
- [WhatsApp OTP vs SMS OTP: cost per verified user, with a calculator](https://mobilevalidate.com/blog/whatsapp-otp-vs-sms-otp-cost.md) — 2026-09-25 · Deliverability: WhatsApp authentication rates vs SMS prices by country, the October 2026 changes, and a calculator for cost per verified user including SMS fallback.
- [Why SMS messages aren't delivered: a cause tree with fixes](https://mobilevalidate.com/blog/why-sms-is-not-delivered.md) — 2026-09-25 · Deliverability: A cause tree for undelivered SMS: invalid numbers, unreachable phones, wrong line types, carrier filtering and handsets, with a fix for each.

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