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Review of Karbonn A21 – Rajib's Blog Rajib's Blog

Review of Karbonn A21

Inside the Karbonn A21

This probably is the shortest review on my blog. Simple reason being the phone’s similarity to it’s sibling – the Karbonn A9+, which has been reviewed extensively on this blog.


The principal difference between the A21 and the A9+ is the larger screen on the A21. While the A9+ display measures 52 mm x 87 mm (4524 sq. mm area), the A21 display measures 56 mm x 99 mm (5544 sq. mm area). Thus the A21 features a hopping 22% bigger display area. Resolution wise, the A9+ features a resolution of 800 x 480 pixels (384000 pixels area) and the A21 features a resolution of 960 x 540 pixels (518400 pixels area) which turns out to be a even bigger 35% more number of pixels.


Compared to the display of the A9+, the A21 display is not as good. The screen test of the A9+ reveals gray shades that are uniform and neutral. The same test run on the A21 results in gray shades that are distinctly colored in hues of red, green and blue. The contrast range in A9+ is also superior with clear bands visible from Contrast of 0% – 100%. The A21 display does not show the darkest two bands with enough separation.


The A21 also features a Li-Ion battery with slightly higher capacity (1800 mAh, versus 1420 mAh battery on the Karbonn A9+).  The additional capacity should help because the phone has a larger display to power. In reality, the battery does even more. I have been installing apps on the phone for over an hour (over WiFi) and the drop in battery is very reasonable when compared to the A9+ (which becomes alarmingly low in the same period with the same activity).

Note that if the battery gets deeply discharged, the phone may not power-up even with the charger connected. In fact, it may not even appear to be charging. Just leave it connected to the charger. In a few minutes, the battery will charge sufficiently and the battery charging animation will show. At this point, you can power on the phone.


It is interesting to note that the battery of A9+ and A21 are not interchangeable. Though they share the same length-width, the the A21 battery is slightly thicker and the contacts of the battery are slightly offset so that it will not work if inserted into the A9+. More number of unique battery designs is generally not good for customers. If Karbonn stops making replacement batteries (don’t know if they even sell replacement batteries), customers would be left in the cold. It also appears that Karbonn’s support telephone numbers do not work.

The world has barely standardized on mobile-phone chargers. It is high-time that some sort of standardization occurs in battery design too.

Other Issues


The A21 does seem to suffer a little more from network problems than the A9+. While my A9+ worked merrily throughout my house on the really poor BSNL network, the A21 behaved more normally and disconnected my calls half-way through the conversations. 😉


Golden Hour image (871KB)

While some buyers have complained of creaky back-cover and touch-screen issues when the phone is plugged in, I actually did not face these. The back-cover on my phone is snug and creak-free. The back-cover of my A9+ on the other hand is creaking.

At times the touch-screen exhibits the same problems that the A9+ does when it is plugged in. Yet at other times, the phone works perfectly. Looks like this phone too suffers from engineering issues with the touch screen and is not completely trouble free.

The micro-switches for Power and Volume Control are covered in a black plastic sheath on the A21. On the A9+, these micro-switches are exposed. Along with touch-screen issues, you may face issues with the volume control where the volume goes up/down as you use the touch screen.

If the touch screen becomes unresponsive and seems to misinterpret your touches, try to restart the phone. You will experience this problem more as you launch and close many applications. Restarting the phone fixes the issue.

Interestingly, the port of the USB charger is upside down in this phone. Please pay attention to this and insert the charger pin in the correct orientation. Forcibly inserting the charger in the incorrect orientation will for sure damage the socket permanently. The volume rocker keys too are on the right side of the phone (versus the left-side of the A9+ and most other phones).


Overcast Weather (1MB)

I had bad product delivery issues. Though the package arrived from FlipKart in record time and seemed unmolested. Upon opening the ‘sealed’ box of the phone, I found oily fingerprints all over the phone screen, oily smudges all over the battery compartment and a clearly re-sealed battery pack. I have a feeling that this is a Karbonn mobiles fault rather than FlipKart’s. Perhaps Karbonn has sold me a refurbished phone for the price of a new unit or perhaps Karbonn employees are not using hand-gloves during manufacturing / packaging of the product.

Also, the phone did not have a screen-guard installed and the box contained only one screen-guard. Other buyers have confirmed that their packages contained additional screen-guards. Maybe the person installing the screen-guard messed up and chose to simply pack the phone with one screen guard (uninstalled).


The phone features the exact same hardware as the A9+ in the imaging department. Consequently, images taken by the cameras are nearly identical. The resolution is barely acceptable. Dynamic range is poor. Focusing speed is acceptable but in low contrast scenes, it requires multiple attempts to focus the camera on the subject before taking the photograph.

I wish these cameras came with a tripod mount; even if it requires a new tripod mount size to be invented for small-size-light-weight cameras.


The phone’s hardware specifications are identical to the Karbonn A9+ and I did not expect too much variation in performance levels. In any case, here are the numbers: (Note that these scores vary marginally every time we run these benchmarks)

Sun Spider Browser Score: 1883.7 ms

(A9+ = 1940.3)

[table “16” not found /]

The phone comes preloaded with a couple of apps likes Yahoo Messenger, WeChat, PayTM, TimesOfIndia, Popi, nexGTV, WhatsApp. These apps cannot be removed from the phone without ‘rooting’ the phone. Some of these apps also start at boot time and eat up precious RAM (phone features 384MB RAM, RAM available after phone restart = 78 MB).

Should You Buy This Phone?

IMHO, the phone is good value for money. Touch-screen issues aside, the phone is usable much of the time and you will hard-pressed to find a phone with such specifications for 10.5K! Remember, there are worse offenders out there.

Download Phone Debug Info

Karbonn A21 Panorama

Panorama Image taken by Karbonn A21 (768 KB)

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35 Responses

  1. Hi Rajib,

    I’ve bought Karbonn A21 tow days ago. I was using DOCOMO & Vodafone, but after inserting both the SIM in A21, it is showing No Service. I’m in Kolkata. I’ve tried searching network but the network isn
    t registering. Sometimes I’m getting signal for few seconds only. Is there any other way I can try.

    Would appreciate your advice..


    • Rajib Ghosh says:

      Dear Subhasish,

      Are the following true?
      1. In the past, at your location, were you able to successfully connect to the Docomo and Vodadfone network with a different phone?
      2. At present, are you able to connect to those networks at your location using a different phone?
      3. Is there any place at all where your A21 behaves normally and connects to the networks?

      If your answer is Yes, Yes & No, then there maybe a manufacturing defect with your phone and I suggest that you get it serviced under warranty.

      Karbonn’s manufacturing seems to be a little hit & miss with my A21 arriving in extremely dirty condition while the A9+ was in pristine condition.


  2. buddha says:

    hi rajib
    i bought this A21,every thing is fine, only no 3G video call from sim or contact, also i could not find ,sign out option in gmail. can u guide me. thanks a lot for ur review on A 9+ and A21. regards.

    • Rajib Ghosh says:

      Dear Buddhadeb,

      The phone does not come with an app for Video-calls over 3G networks. I am not aware of any phone that comes with a cross-platform-model app like that.

      Users are required to use a 3rd party app like Google Chat / Skype / Fring etc. to make video calls. These apps work fine over WiFi and there is no reason why they will not work over 3G. I will be upgrading my SIM to 3G soon and I will perform the video calling test and let the readers know.

      The phone comes with an App called ‘Gmail’. This app is a bit like ‘Thunderbird / Outlook’ program for the PC. The app downloads your emails and makes them available even when you are offline. Quite naturally, there is not Sign-off in this app. If you want to prevent others from opening this app, perhaps you can password protect it by downloading another app from the Google Play Store.

      If you have signed into Gmail using the browser, you can quite easily sign-out. Refer to the screenshot:


      • buddha says:

        dear rajib
        thanks for your information reg A21, one more question is that, when i downloads pdf file from german consulate web site for visa pdf file ,1st it shows succesful after that it shows failed,but the file content kb showing the req KBytes ,.In my phone adobe reader ver 10.4.2 and kingsoft ver 5.3.2 already help me how could i open those pdf file in my phone(in security i have allow installation of non market apps)

        • Rajib Ghosh says:

          Dear Buddhadeb,

          Normally, clicking on the download link should download and save the file. In case this is not successful, just do a long-press (not hard-press) on the link. You should see the “Context Menu” appear with the option “Save Link”.

          Acrobat Reader should be generally be the default PDF reader on the phone. If not, launch the program and check it’s options. Either way, a long-click on any file generally opens the Context menu and a list of the programs that can be used to open the file.

          To be on the safer side, do NOT enable the installation of non-market apps. Google Play has enough freeware options to satisfy most needs and the paid apps are cheap enough to afford.

          Even with a rooted phone, you do not need to install unsigned apps.


  3. Vishvesh says:

    I have used A9+ and A21 both,
    Both Rooted.. I got Everything that an Android Branded Products (Some more things like QPST download and Pre Rooted advantages.. too ;-D)
    The only question that i want to ask is >> What if you want to change FIRMWARE ?
    Is this anyway to use CWM or Customizing Firmware ?
    Regards Vishvesh.

  4. buddhadeb says:

    my dear rajib can give some information about ,nokia n73 (ord) to nokia n73 music edition conversion i.e 2g phone to 3g phone as i have ord nokia n73 which i want to convert 3g supported phone (call from sim /contact). some information are nokia n73(ord) Ver-4.0738.3.1.1 05.12.2007 RM-132 NokiaN 73(23). The 3g enabled Nokia n73 have the Ver-4.0839.42.2.1 27-09-2008 RM-133 Nokia N 73 (12). ie music edition.(the info of n73 music edition received from my friend by *#0000# ) so please give the procedure how to convert the said mobile handset. thanking you, with warm regard. bdc

  5. sajal says:

    dear sir ..
    i have a problem in my karbonn a21 model..i am purchase it just 1 month,,,,.this mobile many time restart when i play hd game,and when i plugged in charger and use it,and the mobile temparatuer autometically increase… i solve this problem

    • Rajib Ghosh says:

      Dear Sajal,

      These behavior are normal. The phone restarts are generally because of low-phone-memory and overdraw of resources. While charging the battery on the phone, the phone can get warm.


  6. klishor bastola says:

    Dear Rajib Gosh sir. I bought Karbonn A21 2 weeks ago. I have found one big issue in touch. When i press home button long time, it doesnot shows the recently used apps and when i try to open the menu of apps touch doesnot work properly and when i press lock button and again i unlocked then only menu apps work but the issue with the home button remains same. My home button doesnot shows the recently used apps… so to close the recently used apps i m having problem with the touch…

  7. mukund says:

    Hi rajib,
    I bought A21 1 week back. i am facing some problem, when i talk, i could hear some echo, as if i am talking in a big hall. Also there are complaints that, my voice on the phone is bit low.
    Did you face any problems like that?

  8. prakash says:

    Dear Rajib Gosh sir. I bought Karbonn A21 1 weeks ago. I have found one big issue in touch. When i press home button long time, it doesnot shows the recently used apps and when i try to open the menu of apps touch doesnot work properly and when i press lock button and again i unlocked then only menu apps work but the issue with the home button remains same. My home button doesnot shows the recently used apps… so to close the recently used apps i m having problem with the touch

    • Rajib Ghosh says:

      Dear Prakash,

      I am not experiencing the issue you are describing. Can you get your phone checked at the service center for manufacturing defects?


  9. Ashish says:

    Rajib Sir,

    I have 3G activated Idea Sim.. I double checked 3G Service on my SIM through other mobile and customer care. Both are saying 3G service is activated on my IDEA SIM. But my Karbonn A9+ does not showing 3G network. I installed the SIM on both the slots and checked all the network related options available in the phone.

    Please tell me what is wrong with me and what setting is needed.



    • Rajib Ghosh says:

      The phone does work with 3G network. Just make sure that the 3G SIM installed in SIM-1 slot.

    • Ashish says:

      Rajib Sir,

      I rushed to the service center for my both problems.

      1. 3G related problem – There was a setting problem. It was in wrong network setting.
      2. Automated SMS problem – They reinstalled operating system of my mobile. Now problem is solved.

      Thanks & regards,


  10. Ashish says:

    Rajib Sir,
    Since I bought my Karbonn A9+ my mobile balance continuously going down without making any call or SMS. I thought Idea Mobile company is cheating me. When I checked my balance deduction details it shows that every day my mobile is sending SMS (mobile is not showing any sent message) without my knowledge and Idea mobile company is charging Rs. 3/- per SMS. My mobile is on factory setting and has no extra software installed. MY Idea mobile connection has no VAS activated.

    Please help me why my Karbonn A 9+ mobile is sending SMS regularly.



    • Rajib Ghosh says:

      Karbonn phones send a SMS message to someone (Karbonn? Google?) when they are first activated.
      It appears that this process is not completing successfully and as a result your phone is repeatedly sending the SMS thus costing you money.

      See if you can show it to the service center. You an typically replicate this error by turning the phone completely Off (remove battery) and then turn it back on in presence of the service center technician.

  11. jayant says:

    Dear Rajib,




    • Rajib Ghosh says:

      Dear Jayant,

      I have a BSNL and Airtel SIM in my phone. In low signal area, the phone keeps searching for network and eventually goes offline (x mark on SIM signal). Once it does that, I have to generally put the phone in “Airplane Mode” (turn on, wait 30 secs, turn off mode) to restart the SIMs.

      This is quite common among SmartPhones where they turn off the GSM Radio to save on battery (in case of low or no signal).


  12. Mohan Silwal says:

    Dear sir my proximity sensor doesnot get calculated. It only says assembly error suspected. What is this???? Could you help me. I also hard reset my phone. But the problem is same.

  13. akhilesh says:

    i have an a21…the 3g slot is not says sim closed and when i try to change it it says switched failed please help

    • Rajib Ghosh says:

      Dear Akhilesh,

      Did you try the standard process of putting your phone in Aeroplane mode and back? It solves quite a few network issues.

      You can also try switching the phone on/off to restart networks.

      Try reinserting the sim cards if the above fail. It should sort out your issues as it does for me.


  14. b.d.chatterjee says:

    dear Rajib ji

    how i can sale my used Android karnbonn A21 mobile without my gmail address in it. pl give me process to deactivate my gmail.thanks a lot.bye.

    • Rajib Ghosh says:


      Why don’t you do a factory reset? That should erase all data from the phone including your gmail ID, contacts on phone etc.
      Remember to take your SD Card out before selling.


  15. William says:

    Karbonn a21 battery is not working..possible to get it anywhere?

  16. Piyush says:

    what battrey is compatible with karbonn a21 in case if there is no replacement battery available

  17. rajneesh says:

    hlo rajib sir my phone is not work properly kuch bhi kolo apne ap kt ho gata keyboard use kro to usme bhi yhi ho raha or hang bhaut kr raha jbki memory bilkul clean hai

  18. rajneesh says:

    sir karbonn a21 phone hai app btaye mai kya kru

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