In Magento 2.3 Admin Theme Configuration Tab is Continous Loading or Favicon or Logo File is Not Uploading.
How to Solve :
This Magento Bug is Overcome BY change Design.config.xml
Go to In Magento root Directory then vendor/magento/module-theme/view/adminhtml/ui_component/design_config_form.xml
Original Code :
Line 57
<field name="head_shortcut_icon" formElement="fileUploader">
<settings>
<notice translate="true">Allowed file types: ico, png, gif, jpg, jpeg, apng. Not all browsers support all these formats!</notice>
<label translate="true">Favicon Icon</label>
<componentType>fileUploader</componentType>
</settings>
Line 154
<field name="header_logo_src" formElement="fileUploader">
<settings>
<notice translate="true">Allowed file types: png, gif, jpg, jpeg.</notice>
<label translate="true">Logo Image</label>
<componentType>fileUploader</componentType>
</settings>
Resolved Code :
line 57
<field name="head_shortcut_icon" formElement="imageUploader">
<settings>
<notice translate="true">Allowed file types: ico, png, gif, jpg, jpeg, apng. Not all browsers support all these formats!</notice>
<label translate="true">Favicon Icon</label>
<componentType>fileUploader</componentType>
</settings>
Line 154
<field name="header_logo_src" formElement="imageUploader">
<settings>
<notice translate="true">Allowed file types: png, gif, jpg, jpeg.</notice>
<label translate="true">Logo Image</label>
<componentType>fileUploader</componentType>
</settings>
Replace New Code with old one, then Refresh cache.
Enjoy Your Development.
Pratik Panchal.