Making a POST request to Google OAuth using WWWForms

Hi, I’m trying to write a WWWForm to make a HTTP POST request to exchange an auth code for an access token. This is my first time working with WWWForms and I would like a bit of guidance.

Google gives an example of the request:

POST /oauth2/v4/token HTTP/1.1
Content-Type: application/x-www-form-urlencoded


I retrieve my auth code using GetServerAuthCode(), and pass that to this function:

    	public IEnumerator GetGoogleAccessToken(string auth_code) {
    		WWWForm form = new WWWForm();
    		Dictionary<string, string> headers = new Dictionary<string, string>();
   		 headers.Add("Host", "");
    		headers.Add("Content-Type", "application/x-www-form-urlencoded");
    		form.AddField("code", auth_code + "&");
    		form.AddField("client_id", client_id);
    		form.AddField("client_secret", client_secret);
    		form.AddField ("redirect_uri", redirect_uri);
    		form.AddField("grant_type", "authorization_code");
    		byte[] rawData =;

    		WWW www = new WWW(token_uri, rawData, headers);
    		yield return www;
  1. Am I suppose to append ‘&’ to the end of all my strings?

  2. Referring to this, section 4: OpenID Connect  |  Authentication  |  Google for Developers
    I believe that my endpoint url should be ? Does that seem correct?

  3. Why is it that when I do not modify headers, I can call WWW(url, form), but when I do, I have to call WWW(url, rawData, headers) ? In other words, how does sending a form differ from sending a byte array?

  4. I’m expecting JSON data to be return. Any examples or suggestions on how I should parse that in C#?

Thank you!

I managed to get a response, albeit an error:

   "error": "invalid_client",
   "error_description": "The OAuth client was not found."

I’m using a Web Application Client ID generated from the Google Developer Console.

Is it possible that I need to encode my URL in some way? I’m simply passing it as a string via client_id

Googled this issue, people report changing the Product name to equal the Project name (In Credentials) will solve this. I have them both the same, but the issue persists.

An feedback would help, thanks!

Not sure you still need this or not.

private IEnumerator GetGoogleAccessToken(string TempKey) {
	Dictionary<string, string> content = new Dictionary<string, string>();
	content.Add("grant_type", "authorization_code");
	content.Add("code", TempKey);
	content.Add("redirect_uri", "REDIRECT_URI");
	content.Add("client_id", "CLIENT_ID");
	content.Add("client_secret", "CLIENT_SECRET");

	UnityWebRequest www = UnityWebRequest.Post("", content);
	yield return www.SendWebRequest();