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explainer
What is proof of presence?
Plain English: what the term means, how buildings use it, and the honest trade-offs between the ways to do it.
What the term means.
Proof of presence is exactly what it sounds like: evidence that a person was physically at a place, at a time. In buildings it answers the oldest question in facilities management - did the work actually happen? A signature or a photo shows that something was written or taken. Proof of presence shows that someone was there, and stayed long enough to do the job.
The gap it fills is trust. Owners pay for work they never see, contractors get blamed for jobs they did do, and workers have no easy way to show they turned up. Everyone holds a piece of the story and nobody holds proof - which is exactly where disputes, and wasted money, come from. Proof of presence closes that gap with one record all sides can rely on.
How buildings use it.
Across cleaning, security and maintenance, proof of presence turns invisible, after-hours work into a record everyone can rely on.
- Cleaning. Verify the overnight clean reached every floor, not just the lobby the manager happens to walk through.
- Security. Confirm the patrol actually walked the rounds, checkpoint by checkpoint, on the nights it mattered.
- Maintenance. Show the scheduled service visit happened, with a time you can hand to an owner or a client.
The ways to do it.
Every approach is a trade-off between cost, effort and how hard it is to fake. Here they are, honestly.
- QR codes. Cheap and universal. The trade-off: a QR code is a picture, so it can be photographed and scanned from anywhere - it proves the code was seen, not that a person stood there.
- NFC tags. A tap on a physical tag is harder to fake than a photo. The trade-off: every checkpoint becomes a task - stop, phone out, tap - and a determined attacker can still copy a tag.
- GPS. Location with nothing on the wall. The trade-off: GPS is coarse and easily spoofed indoors, drifts between floors, and tracks the worker continuously, which raises real privacy concerns.
- BLE beacons. A small battery-powered radio marks the spot, and a phone notices it in passing. The trade-off: beacons cost a little more than a printed code, and need a fresh battery every few years.
How enwitness does it.
enwitness uses BLE beacons, and builds on them deliberately. Detection is passive: the worker’s phone notices the beacon during a shift, with nothing to scan and nothing to stop for. It is a witness, not a tracker - no GPS, and nothing recorded outside a work session. And the record belongs to the building, not the contractor, so it survives a change of cleaner or managing agent.
No single reading is blindly trusted, either: the platform watches for the patterns that fraud creates, like impossible travel between checkpoints or signals that do not add up. Because the checkpoints belong to the building, one set of beacons can serve every contractor who works there - cleaning, security and maintenance all verifying against the same points, each seeing only their own work.
The result is proof of presence that costs the worker nothing to produce and gives the building something it can actually stand on. For how the detection works in detail, see how it works. For what it costs, see pricing.