OpenSpool NFC standard in SimplyPrint
Written By Albert Møller Nielsen
Last updated About 4 hours ago
OpenSpool NFC standard in SimplyPrint
Want to use any filament with smart NFC detection - even on printers that don't officially support it? OpenSpool is an open-source project that combines a simple NFC tag format with DIY reader hardware, letting you bring NFC filament tracking to almost any setup. SimplyPrint fully supports writing OpenSpool tags - and if you build or buy an OpenSpool reader, you can automate filament detection on printers like the Bambu Lab X1.
This article covers everything about using OpenSpool with SimplyPrint. For a general introduction to NFC in 3D printing, hardware options, and step-by-step guides, see our main NFC article.
NFC support in SimplyPrint
SimplyPrint has deep NFC integration across our entire platform - both the web panel and mobile apps for iOS and Android. We support reading and writing NFC tags in multiple formats, allowing you to work with filament from various brands and make your spools work with different printer ecosystems.
What you can do with NFC in SimplyPrint:
- Read NFC tags to instantly identify spools and see their details
- Write NFC tags in various formats - OpenSpool, OpenPrintTag, OpenTag, Creality, QIDI, Anycubic, and more
- Link physical spools to their "digital twin" in your filament inventory
- Quickly assign spools to printers by scanning instead of scrolling through lists
How you can read and write NFC:
- Mobile apps (iOS & Android) - most phones have built-in NFC, making this the easiest method
- Desktop USB readers - for those who prefer working from their computer
For the full breakdown of hardware options, supported methods, and step-by-step guides, check out our main NFC article.
What is OpenSpool?
OpenSpool is more than just an NFC tag format - it's a complete open-source ecosystem for filament tracking. Created by spuder (a community developer), OpenSpool includes both:
- A simple NFC tag format - JSON-based data stored on common NTAG215/216 tags
- DIY reader hardware - ESP32-based readers you can build or buy that communicate directly with your printer
Why is this different?
Most NFC standards are just about the data format - you need the printer's own hardware to read them. OpenSpool flips this around: you build (or buy) a reader that sits next to your printer, and when you touch a tagged spool to it, the reader tells your printer what filament you just loaded.
This means you can add NFC filament detection to printers that weren't designed for it - as long as they support network communication.
Think of it as bringing "smart filament" to printers that don't have built-in NFC readers.
The philosophy
OpenSpool's tagline is "Your filament wants to be free" - and that sums up the project nicely. No proprietary tags, no vendor lock-in, no cloud dependencies. Everything is local and open source.
Official resources
- Website: https://openspool.io/
- GitHub: https://github.com/spuder/OpenSpool
- Discord: Community support available via the project's Discord
- License: Apache License 2.0 (open source)
What can SimplyPrint do with OpenSpool?
SimplyPrint's role is on the tag-writing side of OpenSpool. With SimplyPrint, you can:
- Write OpenSpool NFC tags for any filament in your inventory - stick them on your spools
- Read existing OpenSpool tags - if someone gives you a spool with an OpenSpool tag, we can read it
- Link tags to your inventory - connect physical tags to their digital twin in your filament manager
- Quickly identify spools by scanning - no more guessing which spool is which
What happens after the tag is written depends on your setup:
- If you have an OpenSpool reader connected to your printer, touching the spool to the reader will automatically update your printer's filament settings
- If you don't have a reader, you can still use SimplyPrint's app to scan spools for quick identification and inventory management
For hardware requirements and step-by-step instructions on reading/writing NFC tags, see our NFC hardware & methods guide.
The OpenSpool hardware ecosystem
This is where OpenSpool gets interesting. Unlike other NFC standards where you're dependent on printer manufacturers to add support, OpenSpool gives you the tools to build your own reader.
What is an OpenSpool reader?
An OpenSpool reader is a small device that:
- Sits next to your 3D printer
- Has an NFC reader (PN532 module) to scan tagged spools
- Connects to your Wi-Fi network
- Communicates with your printer via MQTT to update filament settings
When you touch a tagged spool to the reader, it reads the tag data and sends the filament information directly to your printer - no cloud, no apps, just local communication.
Hardware options
Build your own
OpenSpool provides complete schematics, PCB files, and firmware. You'll need:
- Microcontroller: Wemos D1 Mini S3 (or S2)
- NFC reader: PN532 module (configured for SPI mode)
- LED: WS2812B addressable LED for status indication
- Custom PCB: OpenSpool Mini v3.1 (Gerber files provided) - or use a breadboard
Total cost for parts is relatively low if you're comfortable with basic electronics assembly.
Buy a kit
If soldering isn't your thing, the developer sells pre-assembled or kit versions on Tindie. The kit includes:
- Custom PCB
- Microcontroller
- PN532 NFC reader module
- LED and required components
Which printers work with OpenSpool readers?
Currently, OpenSpool readers support:
Even if your printer isn't supported by OpenSpool readers yet, you can still use SimplyPrint to write OpenSpool tags for inventory management and quick identification via our app.
Important: What SimplyPrint can and can't do
Let's be clear about where SimplyPrint fits into the OpenSpool ecosystem:
What works great
Easy tag writing - Create OpenSpool tags for any filament in your SimplyPrint inventory. Stick them on your spools and they're ready to use.iOS and Android support - OpenSpool uses standard NTAG tags, which work perfectly on both platforms.Web NFC support - You can even write OpenSpool tags from a browser on Android devices - no app needed.Cheap, widely available tags - NTAG215 and NTAG216 tags are common and inexpensive.Fast spool identification - Scan any tagged spool with your phone or desktop reader to instantly see which spool it is in SimplyPrint.
What doesn't work
No automatic sync from the printer - This is a general limitation. If your OpenSpool reader updates your Bambu printer's filament settings, SimplyPrint won't automatically know about it. There's no communication back to us.Automatic material syncing - where the printer tells SimplyPrint what's loaded - is currently only available for Bambu Lab AMS (when using Bambu's own tags).You'll need to manually assign spools in SimplyPrint - After loading filament, you'll still need to tell SimplyPrint which spool is on which printer. The good news? With NFC tags, this takes seconds: scan the tag, tap assign, done.No remaining weight tracking - Unlike OpenPrintTag, the OpenSpool format doesn't include fields for tracking remaining filament. The tag stores the same data regardless of how much you've used.
What data does an OpenSpool tag store?
OpenSpool uses a deliberately simple JSON-based format. Here's what's stored:
That's it - simple and focused on what a printer actually needs to know.
Do I need to worry about this format?
Nope! When you write an OpenSpool tag via SimplyPrint, we pull the relevant data from your spool in the filament manager and format it correctly. You don't need to type any JSON or worry about the protocol version.
Why so simple?
OpenSpool was designed with a "do one thing well" philosophy. The format stores exactly what's needed for a printer to set the right temperature and display the right information - nothing more, nothing less. This keeps the tags small and the implementation simple.
What NFC tags does it use?
OpenSpool uses standard NTAG215 or NTAG216 tags. These are:
- Common and cheap - You can buy them from many sources
- Widely compatible - Work with virtually all phones and readers
- Plenty of storage - NTAG215 has 504 bytes, NTAG216 has 888 bytes (OpenSpool data is small, so either works fine)
Where to buy compatible tags
Some links are affiliate links - we may earn a commission at no extra cost to you.
Any NTAG215 or NTAG216 tag will work. You don't need to buy anything special - these are the same tags used for things like Amiibo cards and access badges.
Compatible hardware for writing tags
OpenSpool tags are among the easiest to write because they use standard NTAG tags:
This is one of OpenSpool's advantages - you have lots of options for writing tags, and you don't need expensive specialized hardware.
Why write OpenSpool tags via SimplyPrint?
1. Works with the OpenSpool reader ecosystem
If you've built or bought an OpenSpool reader, tags written by SimplyPrint work perfectly. Touch the spool to the reader, and your Bambu printer (or other supported printer) gets updated automatically.
2. Flexibility to use any filament
OpenSpool doesn't care where your filament came from. Got a great deal on some no-name PETG? Write an OpenSpool tag for it. Using fancy Prusament? Write an OpenSpool tag for it. The reader treats them all the same.
3. Cheap and easy tags
NTAG215/216 tags cost pennies each and are available everywhere. No need to source special proprietary tags.
4. Keep your inventory in sync
When you write tags via SimplyPrint, the spool is already in your inventory. The tag gets linked automatically - no disconnect between physical and digital.
5. Cross-platform friendly
Works on iOS, Android, Web NFC, and desktop readers. You're not locked into any particular device or method.
6. Consistent workflow
Whether you're writing tags for OpenSpool, OpenPrintTag, Creality, or any other standard, the process in SimplyPrint is the same. Learn it once, use it everywhere.
Limitations
OpenSpool's simplicity has some trade-offs:
If you need weight tracking on the tag itself, consider OpenPrintTag instead. If you just want simple filament identification and don't mind the limitations, OpenSpool is great.
OpenSpool vs other standards
How does OpenSpool compare?
OpenSpool's unique strength is the reader hardware - you can add NFC filament detection to printers that weren't designed for it.
Getting started with OpenSpool
Just want NFC tags for inventory?
- Create your filament spools in SimplyPrint's Filament Manager
- Use the app or web to write OpenSpool tags for your spools
- Stick the tags on your spools
- Scan anytime to quickly identify and assign spools
Want automatic printer detection too?
- Build or buy an OpenSpool reader
- Set it up next to your printer and connect to your network
- Configure the reader with your printer's IP and credentials
- Write OpenSpool tags for your spools via SimplyPrint
- Touch spools to the reader when loading - printer settings update automatically
Quick reference
Related articles
- NFC / RFID support in SimplyPrint - Hardware, methods, and step-by-step guides
- The filament manager feature - Managing your filament inventory
- OpenPrintTag standard - Prusa's open NFC standard with more features
- OpenTag standard - Another community open standard