Microchips and GPS trackers get confused often enough that it's worth explicitly separating what each technology actually does, since owners sometimes assume having one means they don't need the other, when they solve genuinely different problems.
Microchips: permanent identification, not tracking
A microchip is a passive, batteryless device that stores an ID number, readable only when a compatible scanner is passed directly over it — it can't be tracked, located remotely, or pinged in real time. Its entire function is providing permanent, tamper-resistant identification once a lost cat is physically found and scanned by a shelter or vet clinic.
GPS trackers: real-time location, not permanent ID
A GPS tracker, typically attached to a collar, actively transmits location data you can view in real time through a connected app — this is genuinely useful for monitoring an outdoor cat's whereabouts or locating a recently escaped cat, but it requires a working battery, a collar that stays attached, and ongoing subscription costs in many cases.
Why you likely want both, not either-or
A GPS tracker can fail (dead battery, lost collar, out of signal range), at which point a microchip remains the reliable backup identification method once your cat is physically located by someone else. Conversely, a microchip alone can't help you actively search for a missing cat the way real-time GPS tracking can.
Registration is the step that actually matters for microchips
A microchip does nothing without current registration — the chip implantation itself is only the first step, and keeping your contact information current in the corresponding registry is what actually enables reunification once a chip is scanned.
Collar-based ID tags remain relevant alongside both technologies
A visible tag with your phone number gives anyone who finds your cat an immediate way to contact you without needing a scanner or GPS app, making this a genuinely useful third layer alongside microchip and any GPS tracking, rather than a redundant addition.