> For the complete documentation index, see [llms.txt](https://rudderlabs.gitbook.io/rudderlabs-1/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://rudderlabs.gitbook.io/rudderlabs-1/docs/stream-sources/rudderstack-sdk-integration-guides/rudderstack-javascript-sdk/js-sdk-faqs.md). # JavaScript SDK FAQs Solutions to some of the commonly faced issues while using the RudderStack JavaScript SDK. This guide contains the answers to some of the commonly-asked questions around setting up, using, and troubleshooting the RudderStack JavaScript SDK. For queries or issues not listed in this guide, you can always start a conversation on our [Slack](https://rudderstack.com/join-rudderstack-slack-community) channel. ## Where do I get the data plane URL? For routing and processing the events to the RudderStack backend, a **data plane URL** is required. Refer to [**this section**](https://docs.rudderstack.com/rudderstack-open-source/installing-and-setting-up-rudderstack/#what-is-a-data-plane-url-where-do-i-get-it) to get the data plane URL depending on your choice of setup. ## How do I load the SDK (`rudder-analytics.js`) correctly? To load `rudder-analytics.js`, follow the instructions in the [**Install RudderStack JavaScript SDK**](https://docs.rudderstack.com/stream-sources/rudderstack-sdk-integration-guides/rudderstack-javascript-sdk/quick-start-guide) section. To check if the library has loaded correctly, open the JavaScript console in your browser: * **Safari**: `Ctrl+Alt+I` (Windows) or `Command+Option+I` (Mac) and go to the `Console` tab. * **Chrome**: `Ctrl+Shift+J` (Windows) or `Command+Option+J` (Mac). * **Firefox**: `Ctrl+Shift+K` (Windows) or `Command+Option+K` (Mac) and select the `Console` tab. * **Internet Explorer**: Press `F12` and go to the `Console` tab. In the console, run `rudderanalytics`. If it returns an object as shown in the following code snippet, it means that the `rudder-analytics.js` file has loaded successfully: ```javascript {Integrations: Object, _integrations: Object, _readied: true, _timeout: 300, _user: n_} ``` If it gives you an `undefined` error, verify if the installation is done correctly. Our [**quick start guide**](https://docs.rudderstack.com/stream-sources/rudderstack-sdk-integration-guides/rudderstack-javascript-sdk/quick-start-guide) may be able to help you get up and running. ## Should I disable ad-blockers on my browser? Yes, it is important that you ensure no ad blockers are running on your browser, as they restrict the`rudder-analytics.js` script from executing and storing user information in the browser. ## Can I load multiple instances of `rudder-analytics.js`? No, it is not possible to load multiple instances of `rudder-analytics.js`, as it is bound to exceed the maximum stack call size and give you an error. ## How to check if the data is being transmitted to the desired destinations? To check if data is being transmitted to the specified destinations, go to the **Network** tab of your JavaScript console in your browser. ![Sample page call](https://876606571-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-Lq5Ea6fHVg3dSxMCgyQ%2Fuploads%2Fgit-blob-54d199fea4a42b9bba0190ccae8e8b7cfe2238d6%2Fjavascript-1.png?alt=media) ![Sample track call](https://876606571-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-Lq5Ea6fHVg3dSxMCgyQ%2Fuploads%2Fgit-blob-d3a447be49b6a5c20ee8ec5dff4bebf9b64304d4%2Fjavascript-2.png?alt=media) If the outbound request is not shown, check if you have installed and set up the RudderStack JavaScript SDK correctly. Also, check if any ad blockers are enabled in your browser. ## What is the size limit on the requests? The size limit on requests is 32KB per message and 4MB per batch request. ## Can I send the event data to specific destinations only? Yes, you can follow any one of the following methods to send your event data to specific destinations: * [Sending events to selective destinations](https://www.rudderstack.com/docs/stream-sources/rudderstack-sdk-integration-guides/rudderstack-javascript-sdk/#loading-selective-destinations): You can send your events only to the selective destinations by stopping the SDK from loading the other [device mode](https://www.rudderstack.com/docs/rudderstack-cloud/rudderstack-connection-modes/#device-mode)integrations. * [Filtering out selective destinations](https://www.rudderstack.com/docs/user-guides/how-to-guides/how-to-filter-selective-destinations/): With this approach, you can stop RudderStack from delivering certain events to the specified destinations. ## What is an anonymous ID? How do I retrieve it? An anonymous ID is an auto-generated **UUID** (Universally Unique Identifier) that gets assigned to each unique, unidentified visitor to your website. To retrieve the anonymous ID of any visitor, call the following: ```javascript rudderanalytics.getAnonymousId(); ``` If the `anonymousId` value is null in the SDK, calling the above function will lead to RudderStack automatically setting a new `anonymousId`. ## What is the `Reserved Keyword` error? When using the JavaScript SDK, you may run into the following error: **Warning! : Reserved keyword used in traits --> id with track call**. This is because one or more of the keys in your `traits` and/or `properties` object is the same value as a reserved keyword. RudderStack has reserved the following keywords as keys for a standard event payload: ```javascript "anonymous_id"; "id"; "sent_at"; "received_at"; "timestamp"; "original_timestamp"; "event_text"; "event"; ``` The above-mentioned keywords should be avoided when naming your event traits and properties. ## Contact us For more information on the RudderStack JavaScript SDK, you can [**contact us**](mailto:%20docs@rudderstack.com) or start a conversation in our [**Slack**](https://rudderstack.com/join-rudderstack-slack-community) community. If you come across any issues while using this SDK, feel free to submit them on our [**GitHub issues page**](https://github.com/rudderlabs/rudder-sdk-js/issues).