> For the complete documentation index, see [llms.txt](https://firstoken.gitbook.io/api-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://firstoken.gitbook.io/api-docs/guides/implementing-captures-sdk-js/migration-and-compatibility.md).

# Migration & Compatibility

This guide ensures smooth transitions between SDK versions and addresses common compatibility concerns.

### Backward Compatibility Promise

**All SDK versions 2.x maintain 100% backward compatibility.** Your existing code will continue to work without any modifications when upgrading.

### No-Risk Upgrade Process

#### Step 1: Update CDN Reference

Simply change your script tag - that's it!

```html
<!-- Before: Any 2.x version -->
<script src="https://cdn.firstoken.co/captures/js/2.1/sdk.js"></script>
<!-- or -->
<script src="https://cdn.firstoken.co/captures/js/2.2/sdk.js"></script>

<!-- After: Latest version -->
<script src="https://cdn.firstoken.co/captures/js/2.3/sdk.js"></script>
```

#### Step 2: Test Your Implementation

Your existing code should work unchanged:

#### Step 3: Enjoy New Features (Optional)

New features are available when you're ready to use them. Implement JWT only when you need enhanced security.&#x20;

To encrypt payload data sent to us, please contact support to enable this feature on your inbound route.

### Support Timeline

* 2.3: Active development
* 2.2: Full support
* 2.1: Maintenance mode