materik materik - 4 months ago 400x
iOS Question

Can't set headers on my WKWebView POST request

I want to do a POST request to my

but the headers doesn't get set when I monitor the requests with Charles so the request fails. What is wrong here?

NSString *post = [NSString stringWithFormat: @"email=%@&password=%@", email, password];
NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
NSString *contentLength = [NSString stringWithFormat:@"%d", postData.length];

NSURL *url = [NSURL URLWithString:@""];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request setHTTPMethod:@"POST"];
[request setHTTPBody:postData];
[request setValue:contentLength forHTTPHeaderField:@"Content-Length"];
[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
[request setValue:@"application/json" forHTTPHeaderField:@"Accept"];

[webview loadRequest:request];

And this is what Charles says the request is like:

POST /endpoint HTTP/1.1
Content-Type: application/x-www-form-urlencoded
Origin: null
Connection: keep-alive
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
User-Agent: Mozilla/5.0 (iPhone; CPU OS 8_0 like Mac OS X)
Content-Length: 0
Accept-Language: en-us
Accept-Encoding: gzip, deflate

So, as you can see,
is not
and no request body were sent.

Thanks for any help.


I had the same problem with WKWebView, that I decided to use instead of UIWebView to avoid the pickers crash in iOS 8. There are two ways that I can think of:

  1. Use NSURLConnection to make the request and then fill the WKWebView with it's response data. You can find an example here: (You only need connection:didReceiveData: and connectionDidFinishLoading: from the delegate if you don't use a self signed SSL certificate)
  2. Use a JavaScript to make the POST request. Here is an example:

Create file eg. "POSTRequestJS.html":

            //POST request example:
            //post('URL', {key: 'value'});
            function post(path, params) {
                var method = "post";
                var form = document.createElement("form");
                form.setAttribute("method", method);
                form.setAttribute("action", path);

                for(var key in params) {
                    if(params.hasOwnProperty(key)) {
                        var hiddenField = document.createElement("input");
                        hiddenField.setAttribute("type", "hidden");
                        hiddenField.setAttribute("name", key);
                        hiddenField.setAttribute("value", params[key]);



And in your code after where you want to load your request:

NSString *path = [[NSBundle mainBundle] pathForResource:@"POSTRequestJS" ofType:@"html"];
NSString *html = [[NSString alloc] initWithContentsOfFile:path encoding:NSUTF8StringEncoding error:nil];
WKWebView.navigationDelegate = self;
[WKWebView loadHTMLString:html baseURL:[[NSBundle mainBundle] bundleURL]];

Add method:

- (void)makePostRequest
    NSString *postData = [NSString stringWithFormat: @"email=%@&password=%@", email, password];
    NSString *urlString = @"";
    NSString *jscript = [NSString stringWithFormat:@"post('%@', {%@});", urlString, postData];

    DLog(@"Javascript: %@", jscript);

    [WKWebView evaluateJavaScript:jscript completionHandler:nil];

    didMakePostRequest = YES;

And last add the WKNavigationDelegate:

- (void)webView:(WKWebView *)webView didFinishNavigation:(WKNavigation *)navigation
    if (!didMakePostRequest) {
        [self makePostRequest];