Crowdin In-context feature fails with CORS error

We are trying to make the Crowdin In-context feature for our tool, but we hit an issue when language is changed to Crowdin In-context.

When I am using the feature from a Remote desktop machine – I got this error:

Crowdin In-Context: Opps. Could not load data from remote server.

Error in console:
Access to XMLHttpRequest at '' from origin 'tool adderss' has been blocked by CORS policy: Request header field traceparent is not allowed by Access-Control-Allow-Headers in preflight response.

This issue occurs only when the project has 5000+ translation strings and is also using App Insights.

  • Firstly the “5000+ translations” changes the way the Crowdin library creates data requests from “fetch all” to “fetch currently needed list”.
  • This change in combination with App Insights inserting a traceparent header to the Crowdin request results in the above-mentioned error.

To fix this, just add to excludeDomains list of applicationInsights config.

Hi @jiri.macek ! Thank you so much for sharing your investigations. Appreciate it so much!