Does web request post have a file size limit?

Unity Engine
,
1

Basically, I encode my texture into byte[ ] using Encode.PNG and I am able to upload a file to the website as JSON, the size of the pictures is 19KB. However, when I tried uploading pictures around 900KB, it showed HTTP 400 bad request. The question here is: does the web request post have a file size limit, or the problem is on the server site. Since the server side is not written by me so I want to know if the problem is with the function. Thanks

IEnumerator UploadImage()
{
    WWWForm form = new WWWForm();
    form.AddField("user_id", "_Pictures");
    form.AddField("data", ImageData);
    using (UnityWebRequest www = UnityWebRequest.Post("Example.com", form))
    {
        www.timeout = 100;
        Debug.Log(www.uploadProgress);
        yield return www.SendWebRequest();
        if (www.result != UnityWebRequest.Result.Success)
        {
            Show_status.text = "Upload failed, please check your internet connection";
            Debug.Log(www.error);
        }
        else
        {
            Show_status.text = "Image upload complete";
            Debug.Log("Image upload complete!");
        }
    }
}
2

First, you are not uploading JSON, where did you get this idea from? You upload HTML form.
There is no limitation in UnityWebRequest, but there might be limitation on server. Files are usually uploaded using multipart form data, not simple form. WWWForm does support multipart forms, see the docs.