Twitter: @mkoehnke
Carthage compatible
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WKZombie is an iOS/OSX web-browser without a graphical user interface. It was developed as an experiment in order to familiarize myself with using functional concepts written in Swift 4.

It incorporates WebKit (WKWebView) for rendering and hpple (libxml2) for parsing the HTML content. In addition, it can take snapshots and has rudimentary support for parsing/decoding JSON elements. Chaining asynchronous actions makes the code compact and easy to use.

Use Cases

There are many use cases for a Headless Browser. Some of them are:

  • Collect data without an API
  • Scraping websites
  • Automating interaction of websites
  • Manipulation of websites
  • Running automated tests / snapshots
  • etc.


The following example is supposed to demonstrate the WKZombie functionality. Let's assume that we want to show all iOS Provisioning Profiles in the Apple Developer Portal.

Manual Web-Browser Navigation

When using a common web-browser (e.g. Mobile Safari) on iOS, you would typically type in your credentials, sign in and navigate (via links) to the Provisioning Profiles section:

Automation with WKZombie

The same navigation process can be reproduced automatically within an iOS/OSX app linking WKZombie Actions. In addition, it is now possible to manipulate or display this data in a native way with UITextfield, UIButton and a UITableView.

Take a look at the iOS/OSX demos in the Example directory to see how to use it.

Getting Started


The best way to get started is to look at the sample project. Just run the following commands in your shell and you're good to go:

$ cd Example
$ pod install
$ open Example.xcworkspace

Note: You will need CocoaPods 1.0 beta4 or higher.


For a Command-Line demo, run the following commands inside the WKZombie root folder:

$ swift build -Xcc -I/usr/include/libxml2 -Xlinker -lxml2

$ .build/debug/Example <appleid> <password>


A WKZombie instance equates to a web session. Top-level convenience methods like WKZombie.open() use a shared instance, which is configured with the default settings.

As such, the following three statements are equivalent:

let action : Action<HTMLPage> = open(url)
let action : Action<HTMLPage> = WKZombie.open(url)
let browser = WKZombie.sharedInstance
let action : Action<HTMLPage> = browser.open(url)

Applications can also create their own WKZombie instance:

self.browser = WKZombie(name: "Demo")

Be sure to keep browser in a stored property for the time of being used.

a. Chaining Actions

Web page navigation is based on Actions, that can be executed implicitly when chaining actions using the >>> or >>* (for snapshots) operators. All chained actions pass their result to the next action. The === operator then starts the execution of the action chain.

The following snippet demonstrates how you would use WKZombie to collect all Provisioning Profiles from the Developer Portal and take snapshots of every page:

>>* get(by: .id("accountname"))
>>> setAttribute("value", value: user)
>>* get(by: .id("accountpassword"))
>>> setAttribute("value", value: password)
>>* get(by: .name("form2"))
>>> submit
>>* get(by: .contains("href", "/account/"))
>>> click(then: .wait(2.5))
>>* getAll(by: .contains("class", "row-"))
=== myOutput

In order to output or process the collected data, one can either use a closure or implement a custom function taking the result as parameter:

func myOutput(result: [HTMLTableColumn]?) {
  // handle result


func myOutput(result: Result<[HTMLTableColumn]>) {
  switch result {
  case .success(let value): // handle success
  case .error(let error): // handle error

b. Manual Actions

Actions can also be started manually by calling the start() method:

let action : Action<HTMLPage> = browser.open(url)

action.start { result in
    switch result {
    case .success(let page): // process page
    case .error(let error):  // handle error

This is certainly the less complicated way, but you have to write a lot more code, which might become confusing when you want to execute Actions successively.

Basic Action Functions

There are currently a few Actions implemented, helping you visit and navigate within a website:

Open a Website

The returned WKZombie Action will load and return a HTML or JSON page for the specified URL.

func open<T : Page>(url: URL) -> Action<T>

Optionally, a PostAction can be passed. This is a special wait/validation action, that is performed after the page has finished loading. See PostAction for more information.

func open<T : Page>(then: PostAction) -> (url: URL) -> Action<T>

Get the current Website

The returned WKZombie Action will retrieve the current page.

func inspect<T: Page>() -> Action<T>

Submit a Form

The returned WKZombie Action will submit the specified HTML form.

func submit<T : Page>(form: HTMLForm) -> Action<T>

Optionally, a PostAction can be passed. See PostAction for more information.

func submit<T : Page>(then: PostAction) -> (form: HTMLForm) -> Action<T>

Click a Link / Press a Button

The returned WKZombie Actions will simulate the interaction with a HTML link/button.

func click<T: Page>(link : HTMLLink) -> Action<T>
func press<T: Page>(button : HTMLButton) -> Action<T>

Optionally, a PostAction can be passed. See [PostAction](#Special- Parameters) for more information.

func click<T: Page>(then: PostAction) -> (link : HTMLLink) -> Action<T>
func press<T: Page>(then: PostAction) -> (button : HTMLButton) -> Action<T>

Note: HTMLButton only works if the "onClick" HTML-Attribute is present. If you want to submit a HTML form, you should use Submit instead.

Find HTML Elements

The returned WKZombie Action will search the specified HTML page and return the first element matching the generic HTML element type and passed SearchType.

func get<T: HTMLElement>(by: SearchType<T>) -> (page: HTMLPage) -> Action<T>

The returned WKZombie Action will search and return all elements matching.

func getAll<T: HTMLElement>(by: SearchType<T>) -> (page: HTMLPage) -> Action<[T]>

Set an Attribute

The returned WKZombie Action will set or update an existing attribute/value pair on the specified HTMLElement.

func setAttribute<T: HTMLElement>(key: String, value: String?) -> (element: T) -> Action<HTMLPage>

Execute JavaScript

The returned WKZombie Actions will execute a JavaScript string.

func execute(script: JavaScript) -> (page: HTMLPage) -> Action<JavaScriptResult>
func execute(script: JavaScript) -> Action<JavaScriptResult>

For example, the following example shows how retrieve the title of the currently loaded website using the execute() method:

>>> browser.execute("document.title")
=== myOutput

func myOutput(result: JavaScriptResult?) {
  // handle result

The following code shows another way to execute JavaScript, that is e.g. value of an attribute:

>>> browser.get(by: .id("div"))
>>> browser.map { $0.objectForKey("onClick")! }
>>> browser.execute
>>> browser.inspect
=== myOutput

func myOutput(result: HTMLPage?) {
  // handle result


Some HTMLElements, that implement the HTMLFetchable protocol (e.g. HTMLLink or HTMLImage), contain attributes like "src" or "href", that link to remote objects or data.
The following method returns a WKZombie Action that can conveniently download this data:

func fetch<T: HTMLFetchable>(fetchable: T) -> Action<T>

Once the fetch method has been executed, the data can be retrieved and converted. The following example shows how to convert data, fetched from a link, into an UIImage:

let image : UIImage? = link.fetchedContent()

Fetched data can be converted into types, that implement the HTMLFetchableContent protocol. The following types are currently supported:

  • UIImage / NSImage
  • Data

Note: See the OSX example for more info on how to use this.


The returned WKZombie Action will transform a WKZombie object into another object using the specified function f.

func map<T, A>(f: T -> A) -> (element: T) -> Action<A>

This function transforms an object into another object using the specified function f.

func map<T, A>(f: T -> A) -> (object: T) -> A

Taking Snapshots

Taking snapshots is available for iOS. First, a snapshotHandler must be registered, that will be called each time a snapshot has been taken:

WKZombie.sharedInstance.snapshotHandler = { snapshot in
    let image = snapshot.image

Secondly, adding the >>* operator will trigger the snapshot event:

>>* get(by: .id("element"))
=== myOutput

Note: This operator only works with the WKZombie shared instance.

Alternatively, one can use the snap command:

>>> browser.snap
>>> browser.get(by: .id("element"))
=== myOutput

Take a look at the iOS example for more information of how to take snapshots.

Special Parameters

1. PostAction

Some Actions, that incorporate a (re-)loading of webpages (e.g. open, submit, etc.), have PostActions available. A PostAction is a wait or validation action, that will be performed after the page has finished loading:

PostAction Description
wait (Seconds) The time in seconds that the action will wait (after the page has been loaded) before returning. This is useful in cases where the page loading has been completed, but some JavaScript/Image loading is still in progress.
validate (Javascript) The action will complete if the specified JavaScript expression/script returns 'true' or a timeout occurs.

2. SearchType

In order to find certain HTML elements within a page, you have to specify a SearchType. The return type of get() and getAll() is generic and determines which tag should be searched for. For instance, the following would return all links with the class book:

let books : Action<HTMLLink> = browser.getAll(by: .class("book"))(page: htmlPage)

The following 6 types are currently available and supported:

SearchType Description
id (String) Returns an element that matches the specified id.
name (String) Returns all elements matching the specified value for their name attribute.
text (String) Returns all elements with inner content, that contain the specified text.
class (String) Returns all elements that match the specified class name.
attribute (String, String) Returns all elements that match the specified attribute name/value combination.
contains (String, String) Returns all elements with an attribute containing the specified value.
XPathQuery (String) Returns all elements that match the specified XPath query.


The following Operators can be applied to Actions, which makes chained Actions easier to read:

Operator iOS OSX Description
>>> x x This Operator equates to the andThen() method. Here, the left-hand side Action will be started and the result is used as parameter for the right-hand side Action. Note: If the right-hand side Action doesn't take a parameter, the result of the left-hand side Action will be ignored and not passed.
>>* x This is a convenience operator for the snap command. It is equal to the >>> operator with the difference that a snapshot will be taken after the left Action has been finished. Note: This operator throws an assert if used with any other than the shared instance.
=== x x This Operator starts the left-hand side Action and passes the result as Optional to the function on the right-hand side.


Once in a while you might need to handle authentication challenges e.g. Basic Authentication or Self-signed Certificates. WKZombie provides an authenticationHandler, which is invoked when the internal web view needs to respond to an authentication challenge.

Basic Authentication

The following example shows how Basic Authentication could be handled:

browser.authenticationHandler = { (challenge) -> (URLSession.AuthChallengeDisposition, URLCredential?) in
	return (.useCredential, URLCredential(user: "user", password: "passwd", persistence: .forSession))

Self-signed Certificates

In case of a self-signed certificate, you could use the authentication handler like this:

browser.authenticationHandler = { (challenge) -> (URLSession.AuthChallengeDisposition, URLCredential?) in
	return (.useCredential, URLCredential(trust: challenge.protectionSpace.serverTrust!))

Advanced Action Functions


The returned WKZombie Action will make a bulk execution of the specified action function f with the provided input elements. Once all actions have finished executing, the collected results will be returned.

func batch<T, U>(f: T -> Action<U>) -> (elements: [T]) -> Action<[U]>


The returned WKZombie Action will execute the specified action (with the result of the previous action execution as input parameter) until a certain condition is met. Afterwards, it will return the collected action results.

func collect<T>(f: T -> Action<T>, until: T -> Bool) -> (initial: T) -> Action<[T]>


Note: Due to a XPath limitation, WKZombie can't access elements within an iframe directly. The swap function can workaround this issue by switching web contexts.

The returned WKZombie Action will swap the current page context with the context of an embedded <iframe>.

func swap<T: Page>(iframe : HTMLFrame) -> Action<T>
func swap<T: Page>(then postAction: PostAction) -> (iframe : HTMLFrame) -> Action<T>

The following example shows how to press a button that is embedded in an iframe:

>>> browser.get(by: .XPathQuery("//iframe[@name='button_frame']"))
>>> browser.swap
>>> browser.get(by: .id("button"))
>>> browser.press
=== myOutput

Test / Debug


This command is useful for debugging. It prints out the current state of the WKZombie browser represented as DOM.

func dump()

Clear Cache and Cookies

Clears the cache/cookie data (such as login data, etc).

func clearCache()


WKZombie logging can be enabled or disabled by setting the following Logger variable:

Logger.enabled = false

User Agent

The user agent of WKZombie can be changed by setting the following variable:

browser.userAgent = "Mozilla/5.0 (iPhone; CPU iPhone OS 9_0 like Mac OS X) AppleWebKit/601.1.32 (KHTML, like Gecko) Mobile/13A4254v"


An operation is cancelled if the time it needs to complete exceeds the time specified by this property. The default value is 30 seconds.

browser.timeoutInSeconds = 15.0

Load Media Content

This value is 'true' by default. If set 'false', the loading progress will finish once the 'raw' HTML data has been transmitted. Media content such as videos or images won't be loaded.

browser.loadMediaContent = false

Show Network Activity

If set to true, it will show the network activity indicator in the status bar. The default is true.

browser.showNetworkActivity = true

HTML Elements

When using WKZombie, the following classes are involved when interacting with websites:


This class represents a read-only DOM of a website. It allows you to search for HTML elements using the SearchType parameter.


The HTMLElement class is a base class for all elements in the DOM. It allows you to inspect attributes or the inner content (e.g. text) of that element. Currently, there are 7 subclasses with additional element-specific methods and variables available:

  • HTMLForm
  • HTMLLink
  • HTMLButton
  • HTMLImage
  • HTMLTable
  • HTMLTableColumn
  • HTMLTableRow

Additional subclasses can be easily implemented and might be added in the future.

JSON Elements

As mentioned above, WKZombie as rudimentary support for JSON documents.

Methods and Protocols

For parsing and decoding JSON, the following methods and protocols are available:


The returned WKZombie Action will parse Data and create a JSON object.

func parse<T: JSON>(data: Data) -> Action<T>


The following methods return a WKZombie Action, that will take a JSONParsable (Array, Dictionary and JSONPage) and decode it into a Model object. This particular Model class has to implement the JSONDecodable protocol.

func decode<T : JSONDecodable>(element: JSONParsable) -> Action<T>
func decode<T : JSONDecodable>(array: JSONParsable) -> Action<[T]>


This protocol must be implemented by each class, that is supposed to support JSON decoding.
The implementation will take a JSONElement (Dictionary<String : AnyObject>) and create an object instance of that class.

static func decode(json: JSONElement) -> Self?


The following example shows how to use JSON parsing/decoding in conjunction with WKZombie:

>>> browser.decode
=== myOutput
func myOutput(result: Book?) {
  // handle result



To integrate WKZombie into your Xcode project using CocoaPods, specify it in your Podfile:

source 'https://github.com/CocoaPods/Specs.git'

pod 'WKZombie'

Then, run the following command:

$ pod install


To integrate WKZombie into your Xcode project using Carthage, specify it in your Cartfile:

github "mkoehnke/WKZombie"

Swift Package Manager

To build WKZombie using the Swift Package Manager, add it as dependency to your Package.swift file and run the following command:

swift build -Xcc -I/usr/include/libxml2 -Xlinker -lxml2


How can I use WKZombie and Alamofire in the same project?

When using Alamofire and WKZombie in the same project, you might encounter a collision issue with keyword Result like this:

'Result' is ambiguous for type lookup in this context

This is due to the fact, that both modules use the same name for their result enum type. The type can be disambiguated using the following syntax in that particular file:

import enum WKZombie.Result

From this point on, Result unambiguously refers to the one in the WKZombie module.

If this would still be ambiguous or sub-optimal in some files, you can create a Swift file to rename imports using typealiases:

import enum WKZombie.Result
typealias WKZombieResult<T> = Result<T>

For more information, take a look at the solution found here.


See the CONTRIBUTING file for how to help out. You'll need to run

$ Scripts/setup-framework.sh

in the root WKZombie directory to set up a buildable framework project (WKZombie.xcworkspace).


  • More Unit Tests
  • More examples
  • Replace hpple with more 'Swifty' implementation
  • More descriptive errors


Mathias Köhnke @mkoehnke

More Resources



WKZombie is available under the MIT license. See the LICENSE file for more info.

Recent Changes

The release notes can be found here.