WebView DevTools is an on-device suite of tools that ships with WebView itself. You can launch WebView DevTools by any of the following:
The best way to launch WebView DevTools is to download WebView Beta, Dev, or Canary. These channels will have a launcher icon which will launch WebView DevTools.
If you have adb installed, you can connect your Android device to launch DevTools:
adb shell am start -a "com.android.webview.SHOW_DEV_UI"
Newer versions of WebView shell have a menu option to launch WebView DevTools. If your copy of WebView shell doesn't have this option, you may need to rebuild it yourself.
Crash UI shows recent WebView-caused crashes from apps on the device, similar to
chrome://crashes. You can access it by tapping the “Crashes” option in the bottom navigation bar.
enable-crash-reporter-for-testing flag from the Flags UI.
Tap a crash entry to expand it for more info and actions for that crash.
Crash reports are automatically reported to WebView's crash collection server. Sometimes a crash report may not be automatically uploaded. For instance, when the device is not connected to Wifi (will show in the crashes list with “pending upload” status). The crash report can also skip upload due to random sampling (will appear with “skipped” status). You can force upload that crash report by pressing the “Upload this crash report” button. After the crash report is uploaded you can then use the upload ID to open a bug report to provide more info about that crash.
While the crash server has most of the information we need to solve issues, it is helpful if you can provide additional details in a bug report, such as steps to reproduce the crash. To do so press the “File bug report” button which will open crbug.com in the browser. You can use the bug report template to provide additional info about the crash for the WebView engineering team. Make sure to fill all the relevant fields in the bug report and leave the crash upload ID in the bug description so that the WebView team can effectively investigate the crash.
While WebView supports toggling arbitrary flags on debuggable devices, we also support toggling a curated set of experimental flags/features on production Android devices. We expose these features as part of WebView‘s on-device DevTools. This is similar to Chrome’s
Tap the “Flags” option in the bottom navigation bar. You can scroll through the list to find your desired feature/flag (ex. “highlight-all-webviews”), tap the dropdown (look for “Default”), and tap “Enabled” in the dialog popup. You can enable (or disable) as many flags as you need.
Kill and restart WebView apps so they pick up the new flags.
When you're done, open the notification tray and tap the WebView DevTools notification to go back to the flag UI. Tap “Reset all to default” and kill and restart WebView apps to go back to the default behavior.
Like Chrome, WebView supports A/B experiments and feature rollouts through variations (AKA “field trials” or “Finch”). The flag UI can override the field trial config, either to enable an experimental feature to ensure your app works correctly, or to disable an experiment to determine if this is the root cause for a WebView behavior change breaking your app. Simply tap “Enabled” or “Disabled” in the UI; “Default” means WebView will pick up the random field trial experiment.
If you find an experiment is the root cause for app breakage, please file a bug, mention which experiment, and link to your app's Play Store page for our team to investigate.
You can also use the flag UI to download new field trial configs (“seeds”) more quickly, to verify the next seed will fix app breakage. Enable all of the following:
Restart your app, kill it, and restart it a second time. Your app should be running with the latest WebView variations seed.
If you're intending to launch a feature in WebView or start a field trial (AKA Finch experiment), we highly encourage you to add to the list (ex. CL, CL). After that, update
enums.xml by running
android_webview/tools/generate_flag_labels.py (see this doc for more context).
Exposing your feature this way has several benefits:
Since Android 7 (Nougat), Android supports installing multiple WebView packages side by side and switching between them. After installing the WebView channel you want, launch WebView DevTools, open the three-dotted menu, and select “Change WebView Provider.” This launches the system UI where you can select your new WebView channel.
You can file general bug reports for the WebView engineering team. Launch WebView DevTools, open the three-dotted menu, and select “Report WebView Bug.” Similar to filing bug reports for crashes, this will open the system browser to our bug tracker (requires sign-in), where you can describe the issue.
You can check for WebView updates directly from WebView DevTools. This is handy if you‘ve applied flags, since the Play Store may pause automatic updates while WebView’s persistent service is running.
You can debug WebView even more with Chrome DevTools! For detailed instructions, check out Remote Debugging WebViews.