Summary
NFC stickers sell a dime a dozen. Packs of 10, 20, even 50 can be picked up on Amazon for pocket change. I wanted to scatter them around the house and turn them into physical shortcuts for my Home Assistant automations. However, turns out all NFC tags aren’t the same, and if you get the wrong one, it might not work as intended. It’s a small difference, and often buried in the fine print, but if you don’t check this specification, your NFC tag might end up being useless for what you wanted it to do. It’ll decide what your tag can do, and what it is capable of. Memory size is the entire spec sheet that matters 144, 504, or 888 bytes, and that’s the whole story When it comes to NFC tags, the chips powering them — NTAG213, NTAG215, and NTAG216 — are nearly identical. They run the same NFC Forum Type 2 standard, work at the same 13.56 MHz frequency, and get read by the same phones the same way. The only meaningful difference between them is how much data they can store. The NTAG213 holds 144 bytes of usable memory, the NTAG215 holds 504 bytes, and the NTAG216 tops out at 888 bytes. That’s it. That’s pretty much the whole distinction, but it turns out this single difference is all that matters. To put it in perspective, 144 bytes is enough for a short URL, maybe 130 to 140 characters and nothing else. A tag with 504 or 888 bytes has enough room to store that same URL and additional records layered on top of it, like a vCard, a Wi-Fi credential, or in my case, extra application metadata. Where the memory shortage becomes your problem Not enough room means a dialog, not automation Since my primary use case for NFC tags is triggering Home Assistant automations, I didn’t pay much attention to the memory aspect before ordering mine. However, when you register an NFC tag with the Home Assistant Companion app, the app doesn’t just write a bare URL to the tag. It writes an NDEF URI record pointing to https://www.home-assistant.io/tag/ , and application records that tell Android to launch the Home Assistant app directly instead of going through a browser or triggering a confirmation notification first. Those application records are what let the tag skip straight to running your automation without any extra steps. The catch is that those application records take up additional space apart from the URL itself. If a tag doesn’t have enough memory for all three records that HA writes, the app can only fit the plain URL record. As a result, tapping the tag opens a dialog on Android where you have to allow it to run instead of firing the automation directly. You have to tap that notification every single time before anything happens. So with an NTAG213 tag, you’re essentially betting that 144 bytes is enough for the URL and the app-launch metadata. Sometimes it squeezes in; often it doesn’t, and you end up with that annoying pop-up between your tap and automations — defeating the purpose of using a physical tag in the first place. Step up to something like an NTAG215 with 504 bytes, and there’s plenty of headroom for the URL and both companion records, so the tap fires the automation immediately. One caveat worth knowing: some users on the latest Companion App builds have reported that the confirmation dialog shows up even on tags with plenty of memory, an issue still open on Home Assistant’s Android repo. If your tap-to-automate setup suddenly stops firing instantly after an app update, that’s worth checking before you assume your tag’s chip is the culprit. The advice I wish I’d gotten before ordering A few extra cents buys you an instant tap If you’re buying tags purely to redirect to a webpage or share a social link, an NTAG213 works fine, and honestly, is the better value for its price. But if you’re buying tags specifically to trigger smart home automations or other, more complicated tasks, spend the extra few cents per tag and get NTAG215 or NTAG216 chips instead. It’s a difference of maybe 10 or 20 cents per tag in bulk, which is nothing compared to the annoyance of unlocking your phone, tapping a notification, and waiting for an app to open every time you just wanted your lights to turn on. More importantly, it gives you what NFC tags are designed for in the first place: convenience. One spec decides whether the tap just works Everything else on the listing is noise Every NFC tag listing buries its chip type somewhere in the fine print. That single specification, not the size, shape, or even the price, is what determines whether your tap-to-automate setup feels instant or broken. Check for NTAG215 or NTAG216 specifically if home automation is the goal, and save the NTAG213 tags for simple link-sharing. And even if you end up buying the wrong one, there’s still some use you can find for those tags around the house.