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Debugging Websites in Chrome for iOS

March 25th, 2019

Debugging web pages displayed in Chrome for iOS has always required building the project from source because the release version of WKWebView does not support Safari Remote Debugging. To help bridge the gap of missing developer support, we added the chrome://inspect page in M73 to locally view JavaScript logs. While building Chrome for iOS from source is still the best way to fully debug web pages, we hope that this tool will make it easier to troubleshoot some problems.

Background

When building Chrome for iOS from source, Safari Web Inspector can be used to debug a web page rendered in Chrome. However, this takes a non-trivial amount of effort which includes setting up a Chromium checkout, installing a current version of Xcode, and waiting for the build to complete. Additionally, a Mac with enough disk space to hold the code and tools is required. This barrier to debugging has led to bugs being filed for specific website failures on Chrome for iOS.

These bugs can be difficult to diagnose as they are generally based on a single failure case. Chrome developers most likely don’t know the website application well enough to fully understand what is causing the bug. Often, the reporter has even spent time to build a dedicated test page to more precisely understand the issue. The lack of debugging tools require developers to come up with alternative methods in order to debug their websites. Of course, nothing is wrong with filing bugs, and we certainly don’t want to discourage it, but we do want to improve the web developer experience.

In-app JavaScript Console

Enable JavaScript log collection by navigating to chrome://inspect in Chrome for iOS and leaving that tab open to collect logs. In another tab, reproduce the case for which you are interested. Then switch back to the chrome://inspect tab to view the collected logs.  (Log collection will stop if the chrome://inspect page closes or navigates and logs will be lost as they are not persisted.)

Debugging Websites in Chrome for iOS

Mike Dougherty, Chrome Engineer on iOS