Behind its minimalist API, Prelude acts as a real-time broker and selects the optimal based on your user’s context and history. It also prevents fraud transparently, without requiring any additional configuration.


When you send an OTP code, Prelude starts an authentication lifecycle. Here’s how it works:


Start an authentication

Your user enters their phone number in your application and you send it to us.


Filter-out fraud

We analyze the request and check for fraud using our existing database and the Signals you provided.

If the authentication is suspicious, we don’t send any code.


Send a code

Prelude compares all of the available and send a code using the best one.

If the user didn’t receive the code, you can create another authentication by calling the Authentication endpoint. Prelude then switch to another route to increase the chances of the user receiving the code.


Verify the code

The user receives the code and enters it in your application. You then send it to the Check endpoint. If it’s correct, the endpoint returns a valid status code.

Once an authentication lifecycle has begun, you can inspect it in the dashboard by looking at the Authentications tab or by by searching for it using the search modal.


Prelude partners with many to guarantee the highest possible delivery rate at the lowest possible cost. We also use multiple to reach your users and our routing engine continuously optimize the delivery based on your user’s context and history.

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Fraud prevention

At the heart of Prelude’s fraud prevention system is a powerful machine learning model that assesses the risk level of each authentication in a few milliseconds. It uses dozens of signals relating to each authentication and draws on data from our vast database to predict whether a request is likely to be fraudulent.

Prelude’s system is flexible and responsive, continually learning from new patterns and incorporating your feedback when users are flagged as returning.

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Next steps

Build a fully-functional SMS OTP flow in your application by following the steps below.