I am started a project probably using the ixkio backend for tag verification. I can see that seritag sell the 413 but mention the 424. There isn't much information on the 424 and I'm confused what the differences are and why there's two chips ?
What's the difference between the NTAG413 and NTAG424 ?
There are a number of technical differences between the NTAG424 and the NTAG413. This is both in terms of 'features' but also in terms of the chip construction itself. However, for most use cases which will involve the SUN secure code applications, they work in the same way. If you have been working and developing with the NTAG413, then you can almost certainly just swap and start using the NTAG424.
The NTAG424 will replace the NTAG413. Seritag still have small stock of the NTAG413 which can be useful for development and testing. However, from now on, we will only be stocking and supplying the NTAG424. It's cheaper, better and easier to work with.
Worth noting that there are two variants of the NTAG424. The standard NTAG424 and the the tamper tag version called the NTAG424 TT. The TT version, like the NTAG213 TT, allows the tag to detect a break in a secondary loop of wire.