Prelude
Prelude · Coding
Prelude is an SMS verification API that sends one-time passcodes through SMS, WhatsApp, RCS, Voice, and Email, with built-in SMS pumping protection and coverage in more than 230 regions.
About Prelude
What Is Prelude
Prelude is a verification and trust platform for developer teams. Its core product, Prelude Verify, delivers one-time passcodes and checks phone numbers or emails during signup. Engineers call a few endpoints to send a code, confirm it, and read the result.
The company focuses on a narrow problem that costs consumer apps real money: SMS pumping fraud. Attackers trigger huge volumes of verification messages to premium-rate numbers and the app pays for every one. Prelude bundles carrier, device, and network signals into each send, which cuts down on fake traffic before it reaches the phone bill.
The main limits are scope and commitment. Verify works best for teams that send at meaningful volume, since the pricing is built around per-verification rates and message costs. Smaller projects can still start on the pay-as-you-go tier, but the deeper fraud tooling and support sit in higher plans.
Getting Started
- Create an account at app.prelude.so and pick up free test credits in the dashboard.
- Grab an API token and install the SDK for Node.js, Python, Go, Ruby, or Kotlin/Java.
- Send a verification request by passing the target phone number to the verification endpoint.
- Collect the code the user receives, then check it against the pending verification ID.
- Turn on volume routing and delivery insights once live traffic starts flowing.
Product Information
A quick look at Prelude's pricing, supported platforms, and performance.
Best for
The users, tasks, and scenarios where this tool fits best.
Users
- Backend and mobile developers
- Growth and product teams at consumer apps
- Teams fighting SMS pumping
Tasks
- Phone verification at signup
- Multi-channel OTP delivery
- Fraud screening before verification
Scenarios
- Launching in new markets
- High-traffic signup spikes
- Cutting messaging spend
Key features
Multi-channel OTP delivery
Verify sends one-time passcodes over SMS, RCS, WhatsApp, Voice, and Email, plus Silent Network Authentication. If SMS delivery fails in a region, the same request can fall back to another channel, so users in tough markets still get their code.
SMS pumping protection
The platform bundles carrier, device, and network signals into every send and scores each request for fraud. Fake signups and bot traffic get blocked before a message is triggered, which is the main reason the messaging bill stays under control.
Global coverage in 230+ regions
Prelude connects to 30+ providers across 230+ regions and reports a 95% verification success rate. One API token covers all of them, so teams don't manage separate carrier contracts country by country.
Developer-friendly API and SDKs
The API keeps a familiar endpoint structure, so existing code can often switch providers without a rewrite. Official SDKs cover Node.js, Python, Go, Ruby, and Kotlin/Java, and the dashboard exposes OTP routing, message text, and delivery insights.
Number intelligence and risk scoring
The Intel and Watch products check a number's reachability, line type, and portability, and monitor behavioral signals in real time. Teams use them to catch abuse and trigger step-up checks without adding friction for normal users.
Cost transparency with no message markup
Prelude bills messages at carrier cost and earns from the verification fee instead of inflating SMS rates. Pricing drops with committed volume across all tiers, and the pay-as-you-go option has no minimum commitment.
Pros and cons
Pros
- Multi-channel delivery, including SMS, WhatsApp, RCS, Voice, and Email, covers users that a single channel would miss.
- Fraud screening runs before a message is sent, so blocked fake signups don't add to the messaging bill.
- Free test credits and test numbers let teams integrate and validate the flow before spending.
- SDKs for five languages and a familiar endpoint structure shorten integration time.
- No markup on message costs and volume-based discounts keep large-scale usage predictable.
Cons
- Pricing is built around per-verification rates plus message costs, so comparing total spend against a flat-rate provider takes some work.
- The deeper antifraud tooling and Slack support only appear in the Startup plan and above, which limits what free and pay-as-you-go users get.
- Advanced risk scoring depends on data history that grows over time, so new accounts start with less signal.
- Coverage and pricing vary by country, so global cost estimates still need a per-region check.
Frequently asked questions
Prelude is an SMS verification API that sends one-time passcodes and verifies phone numbers and emails. It also bundles fraud protection so fake signups get blocked before they reach the messaging bill.
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