Are the web requests obtained by APM RUM asynchronous or synchronous?

Kibana version :

  • 7.3.2

Elasticsearch version :

  • 7.3.2

APM Server version :

  • APM 7.3.2

APM Agent language and version :

  • js-base 4.5.1

Original install method (e.g. download page, yum, deb, from source, etc.) and version :

  • Provided by Elastic Cloud subscription

Fresh install or upgraded from another version?

  • Upgraded from 7.1.1

Additional information:

  • We are using the Elastic Cloud services, so we are not running our stack locally.


  • Is there any way for me to know that the information I'm seeing is asynchronous or synchronous? Is there any way to filter these two, so I can see the difference?

Hi Kourosh,

Thanks for trying out Elastic RUM agent. When you mean web requests, you are referring to API calls (like Fetch, XHR) or resource requests (JS, CSS, Images etc). For the former (XHR specifically), we set the span property sync to true /false depending on whether XHR is being called synchronously or asynchronously.

For the resource requests, we don't use that flag so it's hard to differentiate.

The UI would be able to provide distinction in the near future. Link to the issue -


I appreciate your feedback!

So for API calls, is the default value true or false?

Is there any other way to differentiate using Elastic or any other external tool?

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