> ## Documentation Index
> Fetch the complete documentation index at: https://docs.gatlio.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Introduction

> Gatlio keeps your recurring revenue steady by catching failed payments at the highest-intent moment — when your subscriber is already inside your app.

## What is Gatlio?

Gatlio is a billing enforcement layer for Stripe-powered SaaS products. When a subscriber's payment fails, Gatlio intercepts their next login with a non-bypassable overlay that requires them to update their card before continuing.

No emails. No grace periods. No revenue leakage.

## How it works

<Steps>
  <Step title="Stripe sends a webhook">
    When a payment fails, Stripe fires an `invoice.payment_failed` event to Gatlio. Gatlio classifies it as a **soft decline** (retriable) or **hard decline** (card rejected outright) and updates the subscriber's status accordingly.
  </Step>

  <Step title="Your app checks the subscriber's status">
    On every authenticated session, your enforcement snippet (or mobile SDK) calls the Gatlio status API with the subscriber's Stripe customer ID.
  </Step>

  <Step title="Gatlio enforces the gate">
    * **Active** — nothing shown, subscriber continues normally.
    * **Warning** — a dismissable banner prompts the subscriber to update their card.
    * **Lockout** — a full-screen overlay prevents all app access until the card is updated.
  </Step>

  <Step title="Subscriber updates their card">
    The overlay loads a Stripe-hosted Payment Element directly. Once the card is updated successfully, the gate dismisses and the session resumes.
  </Step>
</Steps>

## Enforcement surfaces

Gatlio provides four ways to integrate — pick the one that matches your stack:

| Surface                                | Best for                          |
| -------------------------------------- | --------------------------------- |
| [JS snippet](/snippet/overview)        | Web apps — add one `<script>` tag |
| [React Native SDK](/sdks/react-native) | React Native apps                 |
| [Flutter SDK](/sdks/flutter)           | Flutter apps                      |
| [Swift SDK](/sdks/swift)               | iOS / macOS (SwiftUI or UIKit)    |
| [Android SDK](/sdks/android)           | Android (Jetpack Compose)         |

## Prerequisites

* A Stripe account in live mode
* Gatlio account ([sign up here](https://app.gatlio.io/signup))
* Your subscriber's `stripe_customer_id` available at login time