Insect mesh is not a cat screen
The most dangerous assumption in a cat's home is that a fitted fly screen will hold her. Standard insect mesh and its frame are built to keep flies out, not to resist several kilograms of cat launching at a bird on the sill outside. Cats lean, climb, and pounce against screens, frames flex and pop, and the cat follows the mesh out of the window. A cat-safe window needs either a properly secured, sturdy screen designed to bear a pet's weight, a restrictor that limits how far the window opens, or a fixed grille, fitted so there are no loose corners a determined cat can work at.
Where a restrictor is your solution, the gap it allows must be smaller than a cat's head, because a cat who can fit her head through a space will commit her whole body to it. Test every restrictor by trying to move it yourself with real force rather than trusting the fitting at a glance.
Height does not make a window safe, it changes the injury
Cats do not reliably land unhurt, whatever their reputation. A fall from a low window onto concrete, railings, or a fence can break legs and jaws; falls from several storeys cause the pattern of chest, leg, and facial injuries veterinarians see every summer from cats who slipped off sills or through unscreened apartment windows. A cat dozing on a sunny sill is one startle, one insect chase, or one roll in her sleep away from the edge, so any reachable open window in a flat above ground level belongs behind a screen or a restrictor, not behind optimism.
Ground-floor windows carry a different risk rather than none: a cat who gets out through one is loose near roads and dogs, in a panic, possibly in unfamiliar territory if the window is not her usual door. Treat street-facing ground windows with the same hardware discipline.
The tilt-and-turn trap
Windows that tilt inward from the top create a hazard many owners never see until it happens. A cat climbs toward the fresh air at the top, slips down into the narrowing V between the tilted pane and the frame, and becomes wedged by the hips or chest, unable to climb back up the smooth glass. Struggling tightens the trap, and a cat stuck this way for hours while a household is out can be seriously injured or worse. If your home has tilt-and-turn windows, use the fully closed or side-opening position with a restrictor when your cat has access, fit a purpose-made guard over the tilted gap, or keep those rooms' windows shut while she is in them.
Habits that back up the hardware
Screens and restrictors fail when people bypass them, so build the habits too. Keep furniture that forms a launch platform away from unscreened windows where you can, do not leave a window open in a room and shut the cat in with it, and check every screen and latch at the start of warm weather and after window cleaners, painters, or builders have had the windows open and refitted. A screen rehung loosely by someone in a hurry looks identical to a secure one until a cat tests it.
If your cat ever does fall or is found trapped in a window gap, have her examined by a veterinarian the same day even if she walks away apparently sound, since internal injuries and fractures are not always visible in the first hours.
One window rule for the whole household
List which windows have cat-safe screens, which have restrictors, and which simply stay shut when she is in the room, and make sure partners, children, guests, and cleaners all work to the same list. KinsLe's Family Sharing keeps that window-by-window record with your cat's home safety notes where everyone can check it, so a hot afternoon never turns on one person not knowing which window was the forbidden one.