Pleas show us some code.

Hi, thanks for your reply.

I do e.g. in the following way:

 let queryURL = "https://api.ebay.com/buy/browse/v1/item_summary/search?" +
         "q=abitur"
 let options = {
     headers: {
         "Authorization": "Bearer " + auth_token,
         "X-EBAY-C-MARKETPLACE-ID": "EBAY_DE",
         "Accept-Language": "en-US",
         "Content-Type": "application/json",
         "Accept": "application/json",
         "Accept-Charset": "utf-8",
         "Content-Language": "en-US"
     }
 }
 let itemReq = https.get(queryURL, options, (res) => {
     var data = null
     res.on("data", part => {
         data = data === null ? part : data + part
     })
     res.on("end", () => {
         let response = JSON.parse(data)
         resolve(response)
     })
 })
 console.log(itemReq)

It also does not seem to matter what accept-language or content-language I set...

Hmmm... I'm not sure about why, but I wonder if all of those HTML "quot" entities might be getting in the way.

For example, you may need to have exactly this syntax: X-EBAY-C-MARKETPLACE-ID: EBAY_DE

Notice above the colon, then space, then EBAY_DE .

Perhaps also try this (without any "quot"s getting in the way): X-EBAY-C-MARKETPLACE-ID = EBAY_DE

Thanks for your reply! As I stated in the comment (which seems to have disappeared mysteriously...) in the code there are no "quot" things these were inserted by this forum to escape the ". The headers are handled by the nodejs api by giving key-values. After all the Authorization part with the bearer token is working (if I remove it the server will complain) so I guess the handling of the headers is correct. I will attach a screenshot of how this looks unescaped in my code as I am a bit frustrated right now...

I'm not experienced with Javascript. Is the colon and space (": ") in those headers sent in the eBay API request, or are they just delimiters in the code? It might matter for the locale but not for the token.

Actually, have a try with EBAY-DE instead of EBAY_DE.

Disclaimer: I am an eBay employee but the views expressed on this post are mine and do not necessarily reflect the views of eBay Inc.