How can I debug javascript on Android?

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I'm working on a project that involves Raphaeljs. Turns out, it doesn't work on Android. It does on the iPhone.

How the heck to I go about debugging something on the Android browser? It's WebKit, so if I know the version, will debugging it on that full version of WebKit produce the same results?

Ordinal answered 22/2, 2010 at 22:50 Comment(3)

Off topic, but consider checking out Snap.svg. It is the remake of RaphaelJS from the same person. It is recreated without the support of old browsers, so it is faster, the code is cleaner, etc. – Pleo 21/5, 2015 at 12:6

Note for accepted answer: In the Samsung Experience >= 9, if you hasn't found your device, switch USB type to sound connector. – Confectionery 21/4, 2019 at 0:1

Partial duplicate: Is it possible to open developer tools console in Chrome on Android phone? - Stack Overflow – Scoundrelly 3/8, 2020 at 10:33

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Update: Remote Debugging

Previously, console logging was the best option for debugging JavaScript on Android. These days with Chrome for Android remote debugging, we are able to make use of all the goodness of the Chrome for Desktop Developer Tools on Android. Check out https://developers.google.com/chrome-developer-tools/docs/remote-debugging for more information.

Update: JavaScript Console

You can also navigate to about:debug in the URL bar to activate the debug menu and the JavaScript error console with recent Android devices. You should see SHOW JAVASCRIPT CONSOLE at the top of the Browser.

Currently in Android 4.0.3 (Ice Cream Sandwich), the logcat outputs to the browser channel. So you can filter using adb logcat browser:* *:S.

Original Answer

You can use the built in console JavaScript object to print log messages that you can review with adb logcat.

console.error('1');
console.info('2');
console.log('3');
console.warn('4')

Produces this output:

D/WebCore (  165): Console: 1 line: 0 source: http://...
D/WebCore (  165): Console: 2 line: 0 source: http://...
D/WebCore (  165): Console: 3 line: 0 source: http://...
D/WebCore (  165): Console: 4 line: 0 source: http://...

Determining the version of WebKit

If you type javascript:alert(navigator.userAgent) in the location bar you’ll see the WebKit version listed e.g.

In Chrome: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/532.2 (KHTML, like Gecko) Chrome/4.0.221.6 Safari/532.2

On Android Emulator Mozilla/5.0 (Linux; U; Android 1.6; en-us; sdk Build/DRC76) AppleWebKit/528.5+ (KHTML, like Gecko) Version/3.1.2 Mobile Safari/525.20.1

N.B.

Versions of WebKit that are not part of a Safari release have a + after the version number, and their version number is generally higher than the latest released version of WebKit. So, for example, 528+ is an unofficial build of WebKit that is newer than the 525.x version that shipped as part of Safari 3.1.2.

Alwin answered 25/2, 2010 at 15:6 Comment(9)

when oh when will i be able to debug locally on Android for times when I can't do it remotely? – Redeploy 17/12, 2013 at 20:19

Not sure. It wouldn't make much sense on a small device like a phone because the screen real estate would be so limited for a full Web Inspector. On tablets it might make more sense, but they'd have to reimagine the Web Inspector for a touch interface which is a significant effort. Maybe they are working on it but who knows. – Alwin 19/12, 2013 at 19:9

I suspect a first cut without any significant adaptations would be a good start, i.e. allow a significant amount of functionality to be used. Some tablets even have a stylus so mouse events can work the same. – Redeploy 19/12, 2013 at 23:2

What was that about a small device like a phone!?!?!? bestbuy.com/site/samsung-galaxy-view-18-4-32gb-black/… – Vasilek 3/10, 2016 at 20:50

Note from the Chrome for Android remote debugging link: "You should be signed in to Chrome with one of your Google accounts. Remote debugging does not work in Incognito Mode or Guest Mode." Wow, why? – Implosive 19/12, 2016 at 9:56

In the Samsung Experience >= 9, if you hasn't found device, switch USB type to sound connector. – Confectionery 20/4, 2019 at 23:59

This is old and does not seem to be entirely correct anymore. On Android 10 with Chrome 76 o a Pixel 3XL, there is no debug console that I can find. – Feckless 13/8, 2019 at 15:5

If your issue is that you've tried all the instructions, and still can't see your Android device in Chrome's remote devices list, it may be because apparently you have to have adb (or full Android Studio) installed. This worked for me, see android.stackexchange.com/a/127276/307307 – Strepitous 3/10, 2019 at 15:32

Please mention https://mcmap.net/q/99293/-how-can-i-debug-javascript-on-android, it was useful for me. No need for remote debugging, and about:debug trick didn't work for me on the latest Android Chrome at the time of writing. – Kashmiri 19/12, 2019 at 16:7

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Try:

open the page that you want to debug
while on that page, in the address bar of a stock Android browser, type:
```
about:debug 
```
(Note nothing happens, but some new options have been enabled.)

Works on the devices I have tried. Read more on Android browser's about:debug, what do those settings do?

Edit: What also helps to retrieve more information like line number is to add this code to your script:

window.onerror = function (message, url, lineNo){
    console.log('Error: ' + message + '\n' + 'Line Number: ' + lineNo);
    return true;
}

Everyman answered 13/10, 2011 at 7:20 Comment(6)

That linked question finally helped me figure out how to actually display the JS console once it's enabled. – Splatter 26/2, 2012 at 23:38

I have just tried, but the about:debug trick did not work on my Nexus S with ICS 4.0.3. – Countrywoman 21/5, 2012 at 6:39

You should try to navigate to about:debug from within the same tab that you have your current page open. Instead of navigating, it will display "SHOW JAVASCRIPT CONSOLE" at the top. If you try accessing about:debug from a new tab, it won't work. – Review 8/10, 2013 at 5:3

This is the stock browser only, right? I'm trying it in a Chrome for Android beta on KitKat without any luck. (seems KitKat no longer has the stock browser) – Amido 7/3, 2014 at 3:50

This needs an Android stock browser, and it does not work on Chrome :) – Balloon 7/3, 2014 at 12:6

Kitkat stock browser, if your manufacturer uses it, is Chromium. about:debug really forwards to chrome://debug which says "cannot be found" but shows a Debug option in the settings. Some of the options do not go into affect until a new tab is opened afterwards. – Elizabethelizabethan 14/12, 2014 at 5:6

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The http://jsconsole.com ( http://jsconsole.com/remote-debugging.html ) provides a nice way you can use to access the content of you webpage.

Sculptor answered 28/10, 2011 at 2:36 Comment(2)

jsconsole.com no longer supports remote debugging as of Sep 2017. I created a replacement site at jsconsole.net that is free to use :) – Zigzag 5/2, 2019 at 16:40

@StevenLove Your page doesn't work. – Ilsa 4/1, 2022 at 8:26

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I use Weinre, part of Apache Cordova.

With Weinre, I get Google Chrome's debug console in my desktop browser, and can connect Android to that debug console, and debug HTML and CSS. I can execute Javascript commands in the console, and they affect the Web page in the Android browser. Log messages from Android appear in the desktop debug console.

However I think it's not possible to view or step through the actual Javascript code. So I combine Weinre with log messages.

(I don't know much about JConsole but it seems to me that HTML and CSS inspection isn't possible with JConsole, only Javascript commands and logging (?).)

Brail answered 23/5, 2012 at 11:13 Comment(3)

Added a step-by-step guide to weinr on OS X at #13330721 – Schroer 23/7, 2014 at 20:49

I've already tried Weinre and I was not very satisfied with the tool. The log is not really reliable. Some errors are not shown. Even if they're shown, Weinre only displays the error message, without the stack trace. That completely pissed me off. – Milson 28/8, 2017 at 11:7

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Take a look at jsHybugger. It will allow you to remotely debug your js code for:

Android hybrid apps (webview, phonegap, worklight)
Web pages which runs in the default android browser (not Chrome, it supports the ADB extension without this tool)

How this works (more details and alternatives on the projects site, this was what I found to be the best way).

Install the jsHybugger APK on your device
Enable USB debugging on you device.
Plug the Android device into your desktop computer via USB
Run the app on the Android device ('jsHybugger')
Enter the target URL and page in the app. Press Start Service and finally Open Browser
- You'll be presented with a list of installed browsers, choose one.
- The browser launches.
Back on your desktop computer open Chrome to chrome://inspect/
An inspectors window will appear with the chrome debugging tools linked to the page on the Android device.
debug away!

Again, with Chrome on Android use the ADB extension without jsHybugger. I think this already described in the accepted answer to this question.

Fortuneteller answered 23/3, 2013 at 6:28 Comment(4)

Why was this downvoted? It's one of the only tools that supports remote debugging of webViews inside of native apps. – Zoes 18/7, 2013 at 21:20

Because it doesn't say how to do it, except it points you to a whole-project link, so you have to dig it yourself a lot before actually succeeding – Diehard 13/8, 2013 at 6:15

This tool is actually pretty good and solved my problem. Too bad I had to dig around googling for it instead of seeing this answer since someone decided to bury it. (I ended up here first) I'll add some details to improve the this answer, see how this whole SO thing works? – Profusive 4/9, 2013 at 20:33

jsHybugger APK is no longer available on Google Play nor for download. The project is stored here: github.com/dcendents/jsHybugger; but seems not to include the code to generate the APK. – Erdei 17/12, 2018 at 15:3

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FYI, the reason why RaphaelJS doesn't work on android is that android webkit (unlike iPhone webkit) doesn't support SVG at this time. Google has only recently come to the conclusion that SVG support an android is a good idea, so it won't be available yet for some time.

Ecliptic answered 22/1, 2011 at 0:36 Comment(2)

Thanks Ludvig, figured this out not long after the original post, but good follow-up. – Ordinal 24/1, 2011 at 13:58

This is not an answer to the main question, please make this into a comment (or a separate question) and delete this. – Leonardoleoncavallo 30/1, 2015 at 16:23

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Full Chrome remote debugging of Android native browser on a Galaxy S6 on Android 5.1.1:

Enable USB Debugging on phone (Settings, about, rapidly tap build number, developer settings, USB debugging)
Open "Internet"
Navigate to 'about:debug' (you will see an error)
MORE menu > Settings > Debug > Remote Debugging
Attach phone to computer with USB cable
On the phone, in the Internet web browser, open the site you want to debug
Open Chrome on computer
Navigate to 'chrome://inspect'
Click inspect on the browser tab you want to inspect

The Galaxy S5 devices shows in Chrome but the tabs only show after you restart. After restarting and attempting to attach, the mobile browser crashes.

Renatorenaud answered 1/3, 2016 at 23:8 Comment(0)

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Chrome has a wonderful feature that simply takes the actual Android Chrome contents (incl. inspection etc.) onto the PC screen...

Enable USB debugging on the device, maybe you also need to connect once via adb devices to trigger the "allow communication with..." dialogue on the mobile device,
connect the Android device to the PC,
start Chrome on both, and
then navigate to chrome://inspect/#devices on the PC.
Here, the tabs from the mobile phone Chrome are listed and can be inspected.

There's also a detailled manual on the net: https://www.till.net/technologie/html-javascript/remote-web-debugging-unter-android-und-chrome

(found that after adb logcat showed nothing from the browser)

Maragaret answered 23/7, 2019 at 13:36 Comment(0)

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Put into address line chrome://about. You will see links to all possible dev pages.

Swale answered 22/3, 2016 at 16:13 Comment(1)

Yes, but there's nothing for the console – Ichabod 16/12, 2016 at 3:34

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Raphael is not supported on pre 3.0 Android browsers, that's what your problem is. They have no support for SVG graphics. It does have support for canvas though. If you don't need to animate it, you could render the graphics with canvg:

http://code.google.com/p/canvg/

That's how we got around this issue for rendering SVG icons in the default Android browser.

Hashish answered 15/6, 2012 at 17:5 Comment(0)

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The about:debug (or chrome:\\debug both of which say page cannot be found, but enable the Debug menu in the settings) when tried on Chrome or Opera on Android KitKat 4.4.2 on a Samsung Tab

If you have ROOT permissions on your device, you can view the console messages directly on the device. Use an app like CatLog to view the log output - https://play.google.com/store/apps/details?id=com.nolanlawson.logcat&hl=en This will let you view all logcat activity.

In Android KitKat/4.4.2, the browser console is output to the Chromium channel. You could filter by "Chromium" to get all browser activity (include browser's internal activity), or simply filter by "Console" to only see the Browser console log.

chromium [INFO:CONSOLE(3)]  "The key "x-minimal-ui" is not recognized and ignored.", source http://mywebsite.com/ (3)

Thoria answered 8/9, 2014 at 1:14 Comment(0)

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When running the Android emulator, open your Google Chrome browser, and in the 'address field', enter:

chrome://inspect/#devices

You'll see a list of your remote targets. Find your target, and click on the 'inspect' link.

Benzo answered 9/1, 2018 at 6:56 Comment(1)

I don't know why this answer hasn't gotten more recognition. It was incredibly simple and it works for emulator and physical device – Tripletail 13/3, 2019 at 21:28

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You can try YConsole a js embedded console. It is lightweight and simple to use.

Catch logs and errors.
Object editor.

How to use :

<script type="text/javascript" src="js/YConsole-compiled.js"></script>
<script type="text/javascript" >YConsole.show();</script>

Elmiraelmo answered 25/11, 2015 at 22:30 Comment(0)

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My solution is (for the stock browser):

Stock Browser
"consolo.log" into the JS source code
Debug USB enabled
Android SDK
From Android SDK : monitor.bat
Monitor filter as the attached image

Gatian answered 16/3, 2015 at 7:53 Comment(0)

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No one mentioned liriliri/eruda which adds its own debugging tools meant for mobile websites/apps

Adding this to your page:

<script src="//cdn.jsdelivr.net/npm/eruda"></script>
<script>eruda.init();</script>

Will add a floating icon to your page which opens the console.

Allopath answered 22/2, 2021 at 23:15 Comment(0)

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"Kiwi browser" has the same tools as the desktop chrome browser and can debug locally in android - no usb needed. Load the html file and choose "developer tools" in the menu. If you need to restart the debugging, reload the html.

Hafer answered 24/1, 2023 at 2:27 Comment(0)

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Android studio provide all you need to see console.log and other. In logcat just filter to "/Web Console" and you will see your js logs...

If you get any issue you can add this plugin : https://github.com/apache/cordova-plugin-console

Leopardi answered 7/3, 2016 at 10:53 Comment(0)

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If you are looking for non remote options:

On earlier and non rooted Jellybean releases a logcat viewer can be used if android.permission.READL_LOGS is granted via adb once.

On firefox, there is a console addon that reads and shows all app logs and there is also firebug lite.

Ashwin answered 27/8, 2016 at 0:18 Comment(0)

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You can try "javascript-compiler-deva" from npm library by running "npm install javascript-compiler-deva" command and then running the compiler.is using "node compiler.js".

It creates a server at port 8888. You can then hit "http://localhost:8888" and enter your JavaScript code and can see the result of any JavaScript code including "console.log" in phone browser itself.

It is also hosted in "https://javascript-compiler-deva.herokuapp.com/"

Jaejaeger answered 2/8, 2018 at 9:11 Comment(0)

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The local debugging/about:config... options seem not to work in 2020+ chrome/ff/.. browsers anymore.

Another browser with non-remote js console is DevBrowser

or WebInspector (file picker not working)

Helfand answered 2/3, 2020 at 2:54 Comment(0)

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You could try https://github.com/fullpipe/screen-log. Tried to make it clean and simple.

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