I'm trying to implement Sitecore Forms with the NextJS app using this official document https://doc.sitecore.com/xp/en/developers/hd/211/sitecore-headless-development/implement-a-sitecore-form-in-a-jss-next-js-app.html

Since I'm using next js I'm passing sitecoreApiHost={''} as mentioned in the document.

enter image description here

I have also followed this document to create Sitecore Form, created rendering, and added the same on the sample page; https://doc.sitecore.com/xp/en/developers/hd/211/sitecore-headless-development/walkthrough--using-a-sitecore-form-in-jss-applications.html

To simplify I have just added a redirect to the page as an action on Submit button with a couple of input boxes.

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When the new rendering is added to the page for forms and after publishing I'm getting the following error;

'Unexpected token '<', "<!DOCTYPE "... is not valid JSON'

enter image description here

Appreciate any help on this topic, thank you.

  • Can you check Console what are the other errors logged? May 30, 2023 at 2:56
  • Just 404 not found and 'Form submit error SyntaxError: Unexpected token '<', "<!DOCTYPE "... is not valid JSON' May 30, 2023 at 3:52
  • I assume that you are seeing that error because Forms is trying to parse the 404 HTML document as a JSON (since it expects a JSON, not a 404 html response). What happens if you instead use “Save Data” as a submit action?
    – Lala
    Jun 3, 2023 at 0:54
  • Even 'Save Data' gives the same result. Jun 6, 2023 at 0:14
  • I followed the same, added the serverSideRenderingEngineEditOnly="false" sitecore.javascriptservices.app.config and in one more config. and also added the patch of HeadlessSiteAccess processor after TransferRoutedRequest. I am still getting the same error "Unexpected token '<', "<!DOCTYPE "... is not valid JSON" in form submit. Console Error: ![enter image description here](i.sstatic.net/4MWbg.png) Please share any advice on it.
    – Prem Murmu
    Jun 28, 2023 at 12:58

1 Answer 1


Finally, I found the solution which is mentioned here;


Basically, for the newly created app, one more config needs to be added which is serverSideRenderingEngineEditOnly="false" and done.

Check the showconfig.aspx for the above key.

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