Unable to add attachments to features in ArcGIS Online

Description

In ArcGIS Online Map Viewer, attempting to add attachments such as images or PDF files to features in a hosted feature layer fails, and returns the following error message:

Error:   
Something went wrong. Error adding the attachment. Please try again.

Attempting to add the attachments in ArcGIS Online Map Viewer Classic also fails and the following error message is returned:

Error:   
Upload Failed.

In some cases, the following error message is returned instead for ArcGIS Online Map Viewer Classic:

Error:   
File type is not supported.

Cause

The size of the attachment is larger than 10 MB. In ArcGIS Online, each file attached to individual features in a hosted feature layer must not exceed the maximum size of 10 MB. Refer to ArcGIS Online: Allow attachments for more information.

Solution or Workaround

To solve the issue, refer to How To: Attach files larger than 10 MB to features in ArcGIS Online to add attachments in ArcGIS Online.