How to Secure Windows From Break-Ins

What a window latch is actually doing

A standard double-hung window has a cam lock or crescent catch at the meeting rail: you turn it and a cam draws the two sashes together. Its job is to hold the window closed against wind and to seal the draught. It is screwed into relatively soft wood or clipped into a vinyl extrusion, and it resists a determined upward shove on the lower sash much less than people assume. A casement window is better — its multi-point gearing throws hooks or mushroom cams into the frame — but the handle itself is often unkeyed, so a hand through a broken pane simply turns it.

That is the mechanism the whole of this page follows from. The two realistic routes into a window are forcing the sash while the catch holds, and breaking enough glass to reach the catch and open the window properly. Every fix below addresses one or the other, and knowing which one you are addressing is how you avoid spending money on the wrong thing.

Four mechanical fixes, in the order they are worth doing

1. Add a keyed sash lock or a secondary catch. On a double-hung window, a keyed sash lock at the meeting rail or a second catch offset from the first means forcing one point no longer opens the window. Two fixings resist far better than one, and the second one is a few dollars.
2. Pin the travel.Drill a small hole through the inner sash channel and drop in a removable pin or a cut dowel so the lower sash cannot rise more than a few inches. This is the window equivalent of a track screw in a patio door, costs nothing, and still allows ventilation. Keep the pin removable — a window that cannot open is a fire-escape problem, which matters more than the burglary risk on an upstairs bedroom.
3. Fit keyed handles on casement windows.If the multi-point gearing is sound, a keyed handle turns “reach through and open it” into “reach through and find it still locked.” Keep the key nearby but not in the handle, and again, think about escape routes first.
4. Check the frame and the glazing beads. On older vinyl and aluminum units the glazing beads can be on the outside, which means the pane can in principle be removed rather than broken. If yours are external, internally-beaded replacement units are the real fix and nothing else substitutes for it.

What security film does and does not do

Window security film is a polyester laminate applied to the inside of the pane. It does not make glass unbreakable and no reputable manufacturer claims it does. What it does is hold the fragments to the film when the pane breaks, so instead of a hole you get a cracked, sagging sheet that still has to be cut or pushed out of the frame. That changes the failure mode: the attack gets slower, noisier and more visible, which is what deters.

Two things decide whether it is worth it. Thickness — thin decorative film does nothing for security and the products that matter are measurably thicker. And edge retention: film applied only to the glass can be pushed out of the frame as a sheet, which is why the serious installations also bond the film edge to the frame. Judge the product by its published specification, not by the demonstration video.

Then, and only then, the sensing layer

Sensing does not stop anybody. It tells you, and it starts a noise. That is worth a lot, but it is worth more on top of the mechanical work than instead of it. Windows need two different kinds of sensing because the two attack routes look completely different to a sensor.

A contact sensoris two pieces, a magnet and a reed switch, that trip when separated. It catches the window being opened — including by somebody who reached through and turned the catch, which is the attack people forget a contact sensor still catches. It is completely blind to a broken pane that nobody then opens.

A vibration or glass-break sensor catches the pane. Vibration sensors mount on the glass or the frame and react to it being struck; acoustic glass-break sensors listen for the frequency signature of breaking glass across a room. These are different mechanisms with different coverage, and the makers of vibration sensors are explicit that theirs is not acoustic detection. Both are ranked in our glass break sensor roundup, and the contact-sensor field is in our door and window sensor roundup.

A patio slider is a window-sized sheet of glass with a door's hardware, and it has its own geometry problems — narrow stiles, a wide closed gap, a panel that lifts in its track. Those are in our sliding-door sensor roundup and our guide to securing a slider.

Where lighting and cameras fit

Lighting is cheap and it works on the opportunity rather than the window: a dark concealed side passage is the thing that makes a basement window attractive, and a motion light or simply trimming the hedge removes more risk than a better catch does. A camera does not secure a window either — it documents what happened and, if it is visible, changes the calculation before anything happens. The sensible order is mechanical fixes, lighting, sensing, then a camera. Camera positions are worked through in our camera placement guide.

Renting? Three of the four fixes are still available

A pin through the sash channel is a small reversible hole, and many landlords will agree to it in writing. Adhesive-mounted contact and vibration sensors leave nothing behind. A standalone window alarm that sticks to the pane needs no hub, no app and no account, which means nothing to uninstall and nothing to cancel. What you should not do without written permission is change the window hardware or apply film, both of which alter the unit. The renter-specific picks across every category are in our no-drilling lock roundup and our renter camera roundup.

The hardware this guide refers to

The four below are one per layer rather than a ranking: a no-hub pane alarm that needs nothing at all, a slim Thread contact sensor for the window being opened, a combined contact-and-vibration sensor that covers both routes in one body, and an acoustic glass break sensor for a large glazed room. Their prices come live from the Amazon API and were last checked October 15, 2026. Everything in this category is at the sensors hub, and the rubric is at our methodology.