Debug iOS 6+7 Mobile Safari using the Chrome DevTools

iOS 6 comes with built-in support for remote debugging (1 minute screencast). It plays nice with the new Safari Web Inspector which seems to be a 1 year old fork of WebKit Inspector. It misses some features such JS editing and WebSocket frames inspection.

> Safari's Web inspector does use the WebKit remote debugging protocol. However, Safari does not use TCP/HTTP as a transport layer, thus making it incompatible with Chrome.

says Timothy Hatcher (aka Xenon), Apple employe

• What does Safari use for transport layer?
• Can I make a proxy from this mysterious transport layer to HTTP to make it work with Chrome DevTools?

The iOS WebKit Debug Proxy project enables this.

To get started, install with homebrew:

brew install ios-webkit-debug-proxy

Run the simulator (if running simulator):

SIM_DIR=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer
  "$SIM_DIR/Applications/iPhone Simulator.app/Contents/MacOS/iPhone Simulator" \
  -SimulateApplication \
  $SIM_DIR/SDKs/iPhoneSimulator6.1.sdk/Applications/MobileSafari.app/MobileSafari

Run the proxy:

ios_webkit_debug_proxy

Check for errors

Look on the device for an error message:

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

Then check the device for a prompt like this (iOS 7 example: )

> Trust the currently connected computer?

Choose "Trust" and try rerunning the proxy:

ios_webkit_debug_proxy

Open default devtools

Then open http://localhost:9221

The DevTools are, by default, an older version (from Chrome 18 circa March 2012).

Try modern devtools

Due to protocol changes, parts the modern DevTools frontend may not work completely. You can try by opening

chrome-devtools://devtools/bundled/inspector.html?ws=localhost:9222/devtools/pag‌​e/2

where the port and page values are the values you're seeing from http://localhost:9221. Again, this may indeed be buggy.

Read more docs at the ios-webkit-debug-proxy project page.

---

Update: This works with iOS7 as well. Update: Added fresh devtools frontend instructions via patrick.. Update: Changed devtools.html to inspector.html for Chrome 45, and the new ws hack via Scheintod.

According to https://github.com/andydavies/node-iosdriver,

> Safari uses the same debugging commands as Chrome but wrapped as binary plists over RPC rather than JSON over websockets.

So, yes, it would possible to write a proxy.

I found this thread by looking at what TCP connections Safari was making while connected to the MobileSafari inspector, seeing that it was connected to a process called webinspectord and Googling that:

# pgrep -lf /Applications/Safari.app
33170 /Applications/Safari.app/Contents/MacOS/Safari -psn_0_21144617
# lsof -p 33170 | grep TCP
Safari  33170 ryan   16u    IPv6 0x799d5f43b472a241       0t0      TCP localhost:54892->localhost:27753 (ESTABLISHED)
# lsof -i :27753
COMMAND     PID USER   FD   TYPE             DEVICE SIZE/OFF NODE NAME
launchd     371 ryan   42u  IPv6 0x799d5f43b472aa01      0t0  TCP localhost:27753 (LISTEN)
Safari    33170 ryan   16u  IPv6 0x799d5f43b472a241      0t0  TCP localhost:54892->localhost:27753 (ESTABLISHED)
webinspec 33182 ryan    6u  IPv6 0x799d5f43b472aa01      0t0  TCP localhost:27753 (LISTEN)
webinspec 33182 ryan    7u  IPv6 0x799d5f43b181a621      0t0  TCP localhost:27753->localhost:54892 (ESTABLISHED)
# ps p 33182
  PID   TT  STAT      TIME COMMAND
33182   ??  S      0:00.28 /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator6.1.sdk/usr/libexec/webinspectord