When buying used phones off of eBay, Craigslist, or the like, a primary concern of anyone purchasing CDMA devices (Verizon, Sprint, Boost Mobile, Virgin Mobile, etc.) is the status of the phone's ESN (electronic serial number). If a device's ESN is registered as "banned" on its carrier because it has been listed as stolen or is attached to an unpaid account, then that phone cannot be activated on said carrier. Thus, the phone is either useless or has to be activated on a pre-paid carrier, which is generally not all that desirable and drastically decreases a device's worth.

Update: JCase has now released a free version of PocketESN. While it performs all of the same checks as the Pro version, it only works on the phone in which it's installed. Hit the widget at the bottom to grab it.

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Enter PocketESN, a creation from our boy Justin Case that allows you to quickly and easily check the status of a device's ESN by scanning the barcode (or entering the number manually) found beneath the battery. While this app is simple in nature, it's infinitely useful to anyone who often deals in used cell phones, as it will potentially prevent them from being duped by dishonest sellers claiming their device is "clean."

While its $5.99 price tag may seem a bit steep, it's definitely a small price to pay for peace of mind when spending $200-500 for a device. If something like this sounds useful but you would only use it occasionally, JCase is also working on a 99c-per-use version of the app.

Cameron Summerson
Cameron is a self-made geek, Android enthusiast, horror movie fanatic, musician, and cyclist. When he's not pounding keys here at AP, you can find him spending time with his wife and kids, plucking away on the 6-string, spinning on the streets, or watching The Texas Chainsaw Massacre on repeat.

  • Howard Cannon

    I think an app like this should be free for the first use and then you can purchase it for more like 3.99 if you are going to use it again. I think the main reason he decided on that price point is because of businesses that can use it, but there are plenty of consumers who regularly change phones that would be discouraged from buying. Either that or make it .99 for every 10 checks.

    • http://PocketESN.com Justin Case


      I will be reviewing the price point of it this weekend, and I am trying to work out a model for the "one time use consumer" right now (literally, on my other screen I am writing it right now).

      The problem with making it free for the first use, would be people just clearing the data on the app, and using it again. Only way around that, would be a secondary licensing server, outside of Google's. This would increase the total cost even more, and that's not even fool proof.

      My cost was actually pretty high compared to other apps (any idea how hard it is to find a boostmobile phone for testing up here in the boonies lol, had to drive a long ways), I really am trying my best to keep it as reasonable as possible.

      I hope that answer's your questions.

    • Jonathan Longoria

      I agree 100% with this. One-time free use and then pay for further services.

  • William N.

    @Howard Cannon

    If something like this sounds useful but you would only use it occasionally, JCase is also working on a 99c-per-use version of the app.

    Read the whole article :P

    and why would you get a free first use?

    • Howard Cannon

      I read the whole article. My statement was addressed as best he could by Justin himself.

  • Dave_N_NYC

    I support app developers like the next guy but this app is near useless for what he/she is charging when there is a website that does it for FREE.
    For anyone who wants to check if an ESN is clean or not, go here:

    Why pay $6 dollars for what has been free for eons via http://www.checkesnfree.com/ ??

  • caliber

    Where is this getting its data from?

    If I were to buy a used phone, my number one concern on this would be the reliability of the data. Without knowing its reliability, I would still have to call up the relevant carrier, which would really limit this app's usefulness.

    • http://www.AndroidPolice.com Artem Russakovskii

      Agreed, would love to get a clarification on that.

    • http://PocketESN.com Justin Case

      The origin source is the same one the customer service agents are querying.

      • http://PocketESN.com Justin Case

        IE We get it from the carriers themselves, sorry if I am being vague but a "how it works" question is the difference of a unique app, and one with many clones.

        If someone is not happy with the quality of the results, I will gladly refund the app.

  • http://derp.org autoprime

    wow nice.. someone is using the http://checkesnfree.com/ service and now charging money for it...

    • http://PocketESN.com Justin Case

      Thats a bold face lie, I have nothing to do with that site, and we are not using it.

    • Justin Case

      The app does not use a intermediate, it talks directly to the carriers. You obviously didn't look at it at all, but decided to make a false accusation out of the side of your neck.

      I wouldn't send my ESNs to an unknown third party site for what it's worth.

      • Cory

        Side of his neck? Nope, more like out of his a$$....keep up the good work J

    • http://www.AndroidPolice.com Artem Russakovskii

      You do know who Justin Case, aka jcase, is, right? You better have some solid proof before throwing around baseless accusations.

  • Efrain Rosado

    Is a great app Justin keep up the good work

  • http://www.mrcellphoneunlocker.com John Hale

    Great app. Worked one every phone I have tested so far. I will be putting up a review on our youtube channel soon.

  • sgtguthrie

    Nice, thanks jcase! I will certainly be purchasing this app for my next craigslist purchase :-) I say leave it at 6 dollars...it's well worth that when buying a device for a couple hundred dollars in a public place, with cash, from someone you don't know and have never met!

    People need to stop whining about a couple dollars! It's a value meal at mcdonalds! How much time do you think these developers spend coding, then you whine about the price of their labor...really?

    • Justin Case


      Hours spent ??? too many
      Phones purchased to test carriers I didn't have? 3
      Hours driving to find a place that carried boostmobile phones? 2.5


  • john

    Hmm, wonder how reliable the database is for bad esn's. I wouldn't trust it myself when hundreds of dollars are on the line.

    • Justin Case

      The databases are the same ones checked by the carrier, they are accurate as can be.

      • http://www.mrcellphoneunlocker.com John Hale

        Yes, They are. I have personally tested prob over 100 phones by now using this app. and i even tried to call the carriers and perfect match on all.

  • Shon G.

    Dang, $6? If I ever decide to purchase a phone used, I'll be all over this. Even if I just use it one time and it saves me from buying some deadbeats old phone, it will be worth it. Thanks, jcase, keep up the good work. :D

  • duplissi

    6 bucks!?.... ugh no thanks, there are plenty of ways of doing this for free (calling, http://checkesnfree.com/, etc.).. 1 or 2 bucks i could see.

    • Justin Case

      Call up sure, use a ""underground"" 3rd party site, no way.

      • duplissi

        the site is legitimate btw... used it many times buying and selling phones on ebay/craigslist

        • http://PocketESN.com Justin Case

          Considering they are advertising services that are illegal in the US (ESN Changing), I am going to have to disagree with you on that.

    • Jaz

      Yes there may be a site already but with this you have it with you at all times in a more convenient way to use it. Plus when I buy used phones on craigslist most people never give me the esn over the phone or email. So when I meet up with them the scan feature will work perfectly.

  • Jonathan Longoria

    I have a request/added feature with something I know will strike home to many of people from XDA, other sites, and even myself as well. T-Mobile now blacklists phones and there have been people on craigslist/eBay who sell their phones deliberately knowing. Unfortunately, in the case for T-Mobile all they have to do is lapse on the EIP and your once clean phone is now blacklisted. I dunno... this is just some heavy thinking from me.

    • http://PocketESN.com Justin Case

      I will look into it, but GSM networks are another beast

      • Jonathan Longoria

        Awesome! Thank you for the consideration. I'm a GSM network person so that is how I could get real use of this and I figured (if possible) it wouldn't hurt to be able to extend the audience as well.

  • Tomas – University Place, WA

    While I also like the idea of a two versions, multi-use $6 version for the "pros" and another potential version at $1 per use for the occasional user, the cost of $6 would not deter me from getting the app even if I were only planning to use it once - after all that's still less than a couple of cups at Starbucks...

    Thanks, Justin!

  • Jaz

    Justin, forget these fools. If they don't like your price point then they don't have to get it. Its great to see your at least trying to meet people half way on pricing.
    Either way I hope to get the app soon. I have purchased several used phones in the last couple months and its a hassle trying to verify esn over the phone with the carrier.
    Can't wait to try it.

  • SomeGuy

    Wish there was a app like this to check for blacklisted IMEI's on the T-Mobile network.