Add custom headers to layer requests

Question

Is it possible to add custom HTTP headers to every layer request (p.e. WMTSLayer)? I'd like to add the referer header because otherwise the WMTS Service doesn't  delivier the image.

RiccardoKlinger2 · Answer

Unfortunately I wasn't able to alter the Referer item (translated to English):

"Attempt to use a forbidden header was rejected: Referer"

RRubalcava · Answer

In 3.x you can use esriRequest.setRequestPreCallback()

esri/request | API Reference | ArcGIS API for JavaScript 3.17

This will let you modify the request before it is sent.