I tried the Ultralight C the other day on a friends device, and it wasn't working. I raise these concerns because I know the Mifare Classic tags don't work with Blackberry, and I was trying to find a tag that works on majority of devices.
I still haven't tried the Ultralight Tags.
Any information anyone has on this issue would be helpful.
Just tested (Nexus 7 using Android 4.1.1, only tech discovered, and some basic info using this NXP taginfo app). Tags below all work for me. Unfortunately I don't have an UltralightC.
What is not working for your UltralightC? Discovery? Reading back the NDEF info?
Anyone else (yeah, besides me) who comes upon this answer in search of information on NFC tag support om the 2013 Nexus 7 (the FHD, or "Full Hi-Def" model) should know that this 2nd-generation Nexus 7 no longer uses NXP's NFC chip and does not support MIFARE tags!
Just to add our own findings:
We sell NFC tags at zipnfc.com and have found so far that NTAG203 works with every phone on the market. We have also found that Ultralight C IC works with all phones, but the reading distance is much less, so when working with the larger device like the Nexus 7 you have to be right on the antenna at the back, but with the NTAG203 you can be near.
NTAG203 is the favourite these days by far unless you need a larger capacity than 137 characters. With most uses of NFC talking back into the cloud 137 is more than enough in most cases.
Mifare Classic 1K still sells well, but mainly for private use where the phone is known or a specific business use, but when a tag is used for marketing and all phones need to be supported the norm has become the NTAG203...
Nexus 7 contains the same NFC chip (PN544 by NXP Semiconductors) as Nexus S, Galaxy Nexus, Nexus Q, Samsung Galaxy S3, HTC One X and many other Android devices. So all these devices support the tag types in principle (antenna performance may differ, leading to somewhat varying results). Blackberry contains an NFC chip by a different manufacturer. MIFARE Classic is a technology by NXP, so it is supported by NXP's NFC chips, but generally not by other manufacturers.
When choosing a tag type that should work on all (or the majority) of devices, I would choose one that implements one of the standardized tag types by the NFC Forum:
I have tested all these types both with Android devices and with Blackberry and they all work. The main difference between the various types is how much data they can store and how easy the data can be protected from overwriting. Most of the named examples above are generally available from various online vendors.