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Tailgating detection: know when more people walked in than were let in

Every time a door opens, the radar in the GateStride door node counts the people who pass through. The center compares that count with the number of phones authorized for that opening. If more people went through than phones were authorized, it flags a possible tailgate for someone to look at.

By Tom Jin · Updated October 2026 · Early access

One badge, three people, and the log shows one entry

Tailgating is ordinary office politeness. Someone badges in, hears footsteps behind them, and holds the door. Most of the time the person behind is a coworker with a full tray of coffee. Sometimes it is a delivery driver, a former employee whose access was removed last week, or a stranger who simply looked like they belonged. Nobody was rude, nobody stopped them, and the access system recorded exactly one entry.

That gap matters for more than security. The access log is supposed to answer who was in the building. When three people walk in on one credential, the log is wrong about two of them, and it is wrong exactly when you might need it: after a theft, during a dispute about hours, or when you are trying to understand who was on site at a certain time. Card systems generally have no way to know how many people went through. They know the door unlocked.

How GateStride counts and compares

Each door node has a microwave radar presence sensor. Besides confirming that a person is at the door before an unlock (see radar presence), the radar counts people as they pass through. For each opening, the node also knows how many enrolled phones were verified and authorized for that door at that time.

The GateStride center compares the two numbers. If two phones were authorized and two people passed, nothing happens. If one phone was authorized and three people passed, the center flags a possible tailgate on that door, at that time, attached to that opening's record in the audit log.

An alert, not a barrier

GateStride does not stop anyone from walking through a door, and it does not lock a door in someone's face. It never touches free egress, which stays with your certified system. Tailgating detection is an alert. It tells the people responsible for the office that an opening did not match the credentials behind it, so they can decide whether it matters.

That is a deliberate choice. Physical barriers like turnstiles and mantraps are a different class of product with their own safety rules. For a typical office, a reliable flag that someone reviews is often what is wanted, without changing how the doors work for everyone.

It does not identify the extra person

Radar produces no images and cannot tell who a person is. The alert says that more people passed than phones were authorized. It does not say who the extra person was. It names the authorized phones for that opening, which gives you a starting point: you can ask the employee who opened the door who came in with them.

If you need to see who it was, that comes from other tools. An optional door camera records like ordinary CCTV, kept on site, and you can review footage for the time of the flag. Facial recognition is optional and off by default. Some states require employers to tell staff about electronic monitoring, so check your state's notice rules. See privacy by design.

Why this matters in a normal office

Most offices are not high-security sites, but tailgating still shows up in everyday problems. A former contractor walks in behind a friend. A visitor skips reception and goes straight to the floor. A door held open for movers becomes the way in all morning. Each one leaves the access log looking clean when it was not.

Tailgating flags pair well with the rest of GateStride. Instant revoke removes someone's phone access at every door in about a second, and tailgating flags show when a person may be getting in another way. Exit tracking keeps the who-is-inside view honest. Everything runs on your premises, with no GateStride cloud. See how it works.

What to do when the center flags a tailgate

1. Open the flag in the GateStride center. It shows the door, the time, the people counted and the phones that were authorized for that opening.
2. Start with context. A known delivery, a scheduled event or a group arriving for a meeting may explain it, and many flags will be a coworker holding the door.
3. If it is not explained, ask the person whose phone opened the door who came in with them.
4. If you run a door camera, review the footage for that time on your on-site recorder.
5. If the same door or the same pattern keeps coming up, fix the cause: issue visitor passes, enroll people who keep borrowing access, or remind staff about holding the door.

What it does not do

• It is an alert, not a barrier. It does not stop anyone from entering.
• It does not identify the extra person. Radar is non-identifying, and an optional on-site camera is the tool for seeing who it was.
• It counts against authorized phones.
• It is not a life-safety, alarm or emergency-notification system.

Questions

What counts as a tailgate in GateStride?

An opening where the radar counted more people passing through than the number of phones authorized for that opening. The center flags it as a possible tailgate.

Will GateStride lock the door or sound an alarm?

No. It records a flag in the center for someone to review. It does not block entry, and free egress stays with your certified system.

Can it tell me who the extra person was?

No. Radar produces no images and cannot identify anyone. The flag shows which phones were authorized for that opening, and an optional on-site door camera can show who came in.

Will every held door create an alert?

A flag is raised when more people pass than phones were authorized. If both people have enrolled phones and are allowed through that door, the counts match and there is no flag.

Where are tailgating records stored?

In the GateStride center on your premises, in the tamper-evident audit log. There is no GateStride cloud.

Do we have to tell employees about this?

Some states require employers to notify staff about electronic monitoring. Check your state's notice rules. We do not provide legal advice.

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