What is a Device Identifier?
A Device ID is a string of numbers and letters that identifies every individual smartphone or tablet in the world. The ID number itself is stored on the mobile device and it can be retrieved by any app that is downloaded and installed. Apps typically retrieve the ID to use it for identification when talking to servers.
How Do I Find My IDFA (Identifier For Advertising)? (IOS Devices Only)
Unfortunately iOS does not currently provide a way for you to see your device's IDFA (Identifier for Advertising). There are some free apps on the App Store that will display your IDFA. Here are a few we've used that appeared to give the right information at the time we tried them (note that we don't have a relationship with these companies and thus can't vouch that these apps aren't malicious, or that they will give the right information in the future):
My Device ID by AppsFlyer - Whitelist Test Device
Note: If you are interested in your IDFA because you want to request that a company look up and/or delete your personal data, do not use the "Reset Advertising Identifier" button in your Settings app until you've written down, taken a screenshot of, or otherwise remembered your current IDFA. The "Reset Advertising Identifier" button gives you a brand new IDFA, but companies will have your personal data recorded under your old IDFA and won't be able to find your data if you don't know what your old IDFA was!
How Do I Find My GAID (Google Advertising ID)? (Google Play Devices Only)
Please follow these steps to find your GAID (Google Advertising ID). It might also be referred to as an AAID (Android Advertising ID). Note that the exact steps may differ depending on your device and operating system. If you can't figure out the steps for your particular device, please email email@example.com and we'll try to help!
Note: If you are interested in your GAID because you want to request that a company look up and/or delete your personal data, do not use the "Reset advertising ID" button until you've written down, taken a screenshot of, or otherwise remembered your current GAID. The "Reset advertising ID" button gives you a brand new GAID, but companies will have your personal data recorded under your old GAID and won't be able to find your data if you don't know what your old GAID was!
Steps for finding your GAID:
1. Launch the Settings app.
2. Find and click the "Google" entry.
3. Find and click Ads.
4. Your GAID is shown on this page. It might be called "Your advertising ID" or something similar.