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Jun 30, 2025
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Support for Multiple Versions of Analytics.js #7005

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Update troubleshooting.md
prigiattiperrut Sep 4, 2024
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forstisabella Jun 30, 2025
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17 changes: 15 additions & 2 deletions src/connections/sources/catalog/libraries/website/javascript/troubleshooting.md
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Expand Up @@ -20,16 +20,29 @@ Segment also provides a Chrome web extension, [Segment Inspector](/docs/connecti

Solution: [Follow the Analytics.js Quickstart Guide](/docs/connections/sources/catalog/libraries/website/javascript/quickstart/)

## Are you loading two instances of Analytics.js?
## Loading multiple instances of Analytics.js

Note that you *cannot* load Analytics.js twice on the same page, even if you're using different write keys. You might encounter `Uncaught RangeError: Maximum call stack size exceeded`. You can conditionally set the write key based on an environment variable.
### Analytics.js snippet loaded more than once

You cannot load the Analytics.js snippet twice on the same page, even if different write keys are used. Doing so might result in errors like `Uncaught RangeError: Maximum call stack size exceeded`.

However, you can conditionally set the write key based on an environment variable:

Example:
```js
var writeKey;
ENV === 'production' ? writeKey = 'A' : writeKey = 'B';
```

### Multiple Versions of Analytics.js

You can load multiple versions of Analytics.js in the same environment. For example, you could have both a snippet version and an npm version on one page, each with different write keys. This allows the npm library and the browser snippet to coexist without conflicting.

Keep the following limitations in mind:

- **Device-Mode Destination Conflicts**: If you are using the same device-mode destination in both instances (for example, across different write keys), conflicts may occur. This is due to third-party scripts that don't support global instances. To avoid issues, ensure you are not using the same device-mode destination with different write keys.
- **CDN URL Customization:** Segment does not support overriding the CDNURL when using multiple instances of Analytics.js.

## Do you see events appear in your debugger?

When you reload the page, does your debugger show a new [`page`](/docs/connections/spec/page)? You can also check the JavaScript console in the browser and manually fire an event, like an Identify call, which would show up in the debugger.
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