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iOS WebKit Debug Proxy

The ios_webkit_debug_proxy (aka iwdp) proxies requests from usbmuxd daemon over a websocket connection, allowing developers to send commands to MobileSafari and UIWebViews on real and simulated iOS devices.


iOS WebKit Debug Proxy works on Linux, MacOS & Windows.


It's easiest to install with homebrew:

brew install ios-webkit-debug-proxy


It's easiest to install with scoop:

scoop bucket add extras
scoop install ios-webkit-debug-proxy

Note: you also need the latest version of iTunes installed.


Install dependencies available in apt repository:

sudo apt-get install autoconf automake libusb-dev libusb-1.0-0-dev libplist-dev libtool libssl-dev

Build and install dependencies that require more recent versions:

Build and install ios-webkit-debug-proxy:

git clone
cd ios-webkit-debug-proxy

sudo make install


On Linux, you must run the usbmuxd daemon. The above install adds a /lib/udev rule to start the daemon whenever a device is attached.

To verify that usbmuxd can list your attached device(s), ensure that libimobiledevice-utils is installed and then run idevice_id -l.

Start the simulator or device

The iOS Simulator is supported, but it must be started before the proxy. The simulator can be started in XCode, standalone, or via the command line:

# Xcode changes these paths frequently, so doublecheck them
$SIM_APP -SimulateApplication $SDK_DIR/iPhoneSimulator8.4.sdk/Applications/

Enable the inspector

Your attached iOS devices must have ≥1 open browser tabs and the inspector enabled via: Settings > Safari > Advanced > Web Inspector = ON

Start the proxy

  • --debug for verbose output.
  • --frontend to specify a frontend
  • --help for more options.
  • Ctrl-C to quit. Also, the proxy can be left running as a background process.

Using with DevTools

ios_webkit_debug_proxy can be used with many tools such as Chrome DevTools and Safari Web Inspector.

Chrome Devtools

In recent versions of Chrome and Safari there're major discrepancies between Chrome Remote Debugging Protocol and Webkit Inspector Protocol, which means that newer versions of Chrome DevTools aren't compatible with Safari.

Safari Web Inspector

You can use Safari Web Inspector extracted from Webkit sources, e.g. artygus/webkit-webinspector or HimbeersaftLP/ios-safari-remote-debug-kit.

Firefox DevTools via Valence

Another option is mozilla/valence which enables Firefox DevTools to be used with iOS.


View and inspect debuggable tabs

Navigate to localhost:9221. You'll see a listing of all connected devices.

Click through to view tabs available on each, and click through again to open the DevTools for a tab.

Setting the DevTools UI URL

Chrome DevTools UI used as a default frontend:

You can use the -f argument to specify different frontend source, like Chrome's local DevTools, a local Chromium checkout or another URL:

# examples:
ios_webkit_debug_proxy -f chrome-devtools://devtools/bundled/inspector.html
ios_webkit_debug_proxy -f ~/chromium/src/third_party/WebKit/Source/devtools/front_end/inspector.html
ios_webkit_debug_proxy -f

If you use -f chrome-devtools://devtools/bundled/inspector.html, you won't be able to click the links shown in localhost:9222 as Chrome blocks clicking these URLs. However, you can copy/paste them into the address bar.

Just the same, you can apply the appropriate port (9222) and page (2) values below.


The -f value must end in ".html". Due to security reasons, https URLs will not work; use http or force-allow with the URL bar's shield icon. As of Chrome 45, the primary URL changed from devtools.html to inspector.html.

To disable the frontend proxy, use the --no-frontend argument.

Port assigment

The default configuration works well for most developers. The device_id-to-port assignment defaults to:

:9221 for the device list
:9222 for the first iOS device that is attached
:9223 for the second iOS device that is attached
:9322 for the max device

If a port is in use then the next available port will be used, up to the range limit.

The port assignment is first-come-first-serve but is preserved if a device is detached and reattached, assuming that the proxy is not restarted, e.g.:

  1. start the proxy
  2. the device list gets :9221
  3. attach A gets :9222
  4. attach B gets :9223
  5. detach A, doesn't affect B's port
  6. attach C gets :9224 (not :9222)
  7. reattach A gets :9222 again (not :9225)

The port assignment rules can be set via the command line with -c. The default is equivalent to:

ios_webkit_debug_proxy -c null:9221,:9222-9322

where "null" represents the device list. The following example restricts the proxy to a single device and port:

ios_webkit_debug_proxy -c 4ea8dd11e8c4fbc1a2deadbeefa0fd3bbbb268c7:9227


undefined reference to symbol 'log10@@GLIBC_2.2.5'
/usr/bin/ld: ios_webkit_debug_proxy-char_buffer.o: undefined reference to symbol 'log10@@GLIBC_2.2.5'
//lib/x86_64-linux-gnu/ error adding symbols: DSO missing from command line

Run this before make: ./configure LIBS="-lm"

error while loading shared libraries:
ios_webkit_debug_proxy: error while loading shared libraries: cannot open shared object file: No such file or directory

Run sudo ldconfig

ssl sendq retry failed: Undefined error: 0

should only happen with versions > 1.8.5, make sure ios-webkit-debug-proxy is built with same version of libssl that libimobildevice was built with

idevice_id not found

The idevice_id executable may be found as part of the libimobiledevice-utils package.

could not start! success

Remove and rebuild libimobiledevice.

Could not connect to lockdownd (or doesn't work with iOS10+)

Could not connect to lockdownd. Exiting.: No such file or directory. Unable to attach inspector ios_webkit_debug_proxy

Check the device for a prompt to trust the connected computer. Choose "Trust" and try again.

Could not connect to lockdownd. Exiting.: Broken pipe. Unable to attach inspector


Could not connect to lockdownd, error code -<number>. Exiting.

Make sure you're using latest version of ios-webkit-debug-proxy

Inspectable pages list is empty for iOS >= 12.2

Make sure you're using latest version of ios-webkit-debug-proxy

Can not see Simulator
  • Make sure you started simulator before the proxy
  • Check that webinspector switch is enabled (Settings -> Safari -> Advanced -> Web Inspector)
  • Most likely simulator's web inspector daemon listens on ipv6 interface, check that you have ::1 localhost line in /etc/hosts
Building under Rosetta (OS X)

libimobildevice formulae depends on openssl@1.1, which is key-only and requires the following env paths for the build

export PKG_CONFIG_PATH="/usr/local/opt/openssl@1.1/lib/pkgconfig"
export LDFLAGS="-L/usr/local/opt/openssl@1.1/lib"
export CPPFLAGS="-I/usr/local/opt/openssl@1.1/include"
If no luck so far...

Lastly, always try replugging in the USB cable.

IWDP Clients

JSON-formatted APIs are provided for programmatic clients.

See the examples/README for example clients: NodeJS, C, clientside JS, websocket and more.


Alt overview

View the design document for an overview of the source layout and architecture.

License and Copyright

Google BSD license Copyright 2012 Google Inc.

The proxy uses the following open-source packages: