If you are looking for an app to make your device do some task (i.e. enable/disable Wi-Fi/Bluetooth, or launch some apps), we recommend: Trigger (formerly known as NFC Task Launcher) is perfect for private use of NFC Tags.

iPhone and iPad NFC Apps (iOS)

About reading NFC tags with an iPhone, you can find the following applications on iTunes:
NFC TagInfo by NXP, free, compatible with iOS 11, is the official app of the IC manufacturer.
NFC Ideas, free, compatible with iOS 8.1 and later. In order to use the iPhone NFC sensor, you need iOS 11 or later.
Please note that the iPhone is compatible with all NTAG®, MIFARE® and ICODE® chips. The iPhone also can’t detect empty tags, but just those containing an NDEF message.

Windows Phone NFC Apps

On Microsoft Store, you can find the following Apps, all compatible with Windows Phone 8 / 8.1, and Windows 10 Mobile:
NFC Commander allows you to read and write NFC Tags, and to automate some actions on your Phone (Fee App)
NFC Launchit allows you to launch apps installed on your Smartphone (Fee App)
NFC Tag Creator allows you to read and write NFC Tags, and to launch apps installed on your Smartphone, (Paid App)
NFC TagWriter Pro allows you to read and write NFC Tags, (Paid App)
NFC Interactor (Paid App)

BlackBerry NFC Apps

For BlackBerry, we recommend the Smart Tags app, which is free and compatible with BlackBerry Z10, Z30, Porsche Design P9982, Passport, and Passport Silver Edition.

Nokia NFC Apps

For those Nokia phones which don’t run Windows, unfortunately, there is not much choice. It seems the only available app is the aforementioned NFC Interactor, which is not free. According to Steve Litchfield, it would be compatible with different models Symbian, including C7 and N9.

NFC Samsung Apps

In addition to other Android Apps, you can use a Samsung App called “Tags” it is preinstalled in some models.

Encoding NFC Tags with a desktop device (Windows / Mac)

Computers are not equipped with an NFC sensor. Consequently, if you want to encode NFC Tags with a PC or a Mac, first you need to get an NFC encoder. On each product’s page, you can find information about that reader’s drivers and software.

In general, we recommend the following software, which can be downloaded for free, and are compatible with Windows, Mac, and Linux.

TagXplorer Developed in collaboration with NXP (the world leading company in the market for the production of NFC chips), TagXplorer allows performing even uncommon types of encoding, such as password-protection, scan counter, or the encoding of single blocks of the chip.

TagXplorer software works only with handful readers the cheapest one is  OMNIKEY 5022  which cost around £55 (see list below), unfortunately, ACR122U is not not compatibale with TagXplorer.

Advanced Card Systems: ACR1281
HID Global: OMNIKEY 5022
Identiv: uTrust 3700, uTrust 4701, CLOUD 3700
NXP: Pegoda, Pegoda 2

List of all NFC Enabled Smartphones and Tablets