You have decided to get a selective feeder. Then the setup instructions ask a question you weren't expecting: do you want to register your cat by their implanted microchip, or by an RFID tag clipped to their collar?
Most brands gloss over this. They shouldn't. The choice changes how the feeder behaves at every meal — how early the lid opens, whether a nervous cat will approach it, and what happens on the day the collar comes off in the garden.
Here is what actually differs between the two, and how to pick for your household.
They Use the Same Technology
Both an implanted microchip and an RFID collar tag are passive RFID transponders. Neither has a battery. Both sit inert until a reader's field energises them, at which point they broadcast a fixed identification number and go quiet again.
This matters for two reasons. First, neither one can run out of power, so "my cat's chip died" is not a failure mode you need to plan for. Second, neither one tracks your cat or knows where they are. An RFID transponder only answers when something is holding a reader a few inches away from it.
The difference between them is not the technology. It is where the transponder sits, and how far away it can be read from.
The Real Difference: Read Range
An implanted microchip sits under the skin, usually between the shoulder blades. It is about the size of a grain of rice. To read it, the antenna generally has to be within an inch or two. In practice this means the feeder cannot identify your cat until their head and neck are already inside the opening.
An RFID collar tag hangs at the throat. It is the same kind of transponder in a small plastic fob, and because it is not surrounded by tissue, feeders can usually read it from considerably further away — often a foot or more.
That difference produces two completely different mealtime experiences:
- With a chip, the cat approaches a closed bowl, puts their head in, and the lid opens. The cat has to commit before they get anything.
- With a tag, the bowl is often already open by the time the cat arrives. Nothing moves near their face.
Neither is better in the abstract. Which one suits you depends entirely on your cat.
When the Implanted Microchip Is the Better Choice
Your cat refuses to wear a collar. Some cats never accept one. Some get genuinely distressed. A chip is already there and needs no cooperation.
Your cat goes outdoors. Properly fitted cat collars are breakaway by design — they are supposed to release under pressure so a cat caught on a branch can free themselves. That safety feature means outdoor cats lose collars, and a lost collar is a cat that cannot eat until you find the spare tag.
Your cat is a determined escape artist indoors. Some cats can get a breakaway collar off within a day, every day.
You want zero ongoing cost. The chip is already paid for. Replacement tags are cheap, but they are a recurring small expense if your cat loses them regularly.
When the RFID Collar Tag Is the Better Choice
Your cat isn't microchipped. This is the obvious one. A tag lets you start today instead of scheduling a vet visit.
Your cat's chip uses a protocol the feeder can't read. This is the trap nobody warns you about, and it is worth its own section below.
Your cat is nervous about the feeder. This is the most common reason people switch. A cat that has been startled once by a lid will often refuse to put their head into a closed bowl again. A collar tag opens the bowl from a distance, so the cat never has to push into a closed space. If you are fighting this battle, see My Cat Is Afraid of the Feeder Lid.
Your cat's chip has migrated. Chips can drift from the shoulder blades down toward the leg or chest over the years. A migrated chip still works for identification at the vet, who can sweep the whole body with a wand. It works far less well for a feeder with a fixed antenna in one spot.
You foster, or your household composition changes. Tags can be reassigned. If cats are moving through your home, tags are dramatically less work than getting each arrival scanned and re-registered.
The Compatibility Trap: Not All Chips Are the Same
An implanted microchip is not a single universal standard, and this is where setups fail.
The international standard is ISO FDX-B, operating at 134.2 kHz. Most chips implanted today, in most countries, are FDX-B. Essentially every selective feeder reads them.
But there are older formats still in living cats, particularly in the United States — 125 kHz chips (commonly associated with AVID) and 128 kHz chips (commonly associated with Trovan and Destron). Whether a given feeder reads those varies by brand and model. If your cat was chipped a long time ago, or was chipped in a shelter using donated stock, do not assume.
Before you buy, find out two things: which protocols the feeder reads, and which protocol your cat's chip uses. Your vet can scan your cat and tell you the number; the format is usually inferable from the digit count and the registry. A 15-digit number is the ISO format.
If your cat's chip turns out to be an unsupported protocol, that is not a dead end. It is simply a household that should use collar tags.
You Do Not Have to Pick One for the Whole House
This is the part most people miss. In a multi-cat household, identification is registered per cat, not per home.
Your chipped indoor cat can be registered by chip. Your unchipped rescue can wear a tag. The nervous one who will not approach a closed lid can wear a tag so their bowl opens before they arrive. You can mix freely, and you can change your mind about any individual cat without disturbing the others.
The Aiwan Cat Food Shield works either way — it reads each cat's implanted microchip or an RFID tag, and sits over the bowl or automatic feeder you already own rather than replacing it. Registering one cat by chip and another by tag is a normal setup, not a workaround.
Where Both Options Fall Short
Worth being honest about the limits.
Neither solves a determined body-blocking cat. If one cat physically shoves another away from an open bowl, identification doesn't help — the lid is open for the authorised cat and the bully is simply taking the space. That is a behavioural and placement problem. See Cat Aggressive About Food.
Neither is instant. There is a brief delay while the transponder is read. With a chip, some cats notice it. Most stop noticing within a couple of weeks.
Metal interferes with RFID. A metal bowl, a metal shelf, or a radiator directly behind the feeder can degrade reads with either method. If reads are unreliable, move the whole setup before you assume the chip is at fault.
Frequently Asked Questions
Can I register a cat by both their chip and a tag? On most systems, yes — a feeder stores multiple IDs, and they do not have to belong to different animals. Registering both gives you a fallback if the collar comes off. It is a good default for a cat that loses collars.
Does the feeder read the chip through my cat's fur? Yes. RFID passes through fur, skin, and tissue without difficulty. What limits it is distance, not the fur. A very thick-coated or heavy cat effectively holds the chip slightly further from the antenna, which can shorten the usable range.
Do RFID collar tags need batteries? No. They are passive, like the implanted chip. They work until they are physically lost or broken.
My cat lost their tag. Can they still eat? Not from a bowl registered only to that tag. Keep a spare — this is the single most common gap in tag-based setups. If your cat loses collars often, register their chip as well.
Is it safe to microchip an adult cat just to use a feeder? Microchipping is a routine procedure that vets perform at any age, and the identification benefit stands on its own regardless of feeding. That said, if the only reason is the feeder, a collar tag achieves the same thing with no procedure. Discuss it with your vet rather than deciding on our word.
Related reading: What Is a Microchip Cat Feeder and How Does It Work? · Do Microchip Cat Feeders Actually Work?
If you are setting up selective feeding for cats with different identification situations, the Aiwan Cat Food Shield lets you register each cat however suits them — chip or tag — on the bowls you already use.