TL;DR
Both clean glass well. Ammonia cuts greasy film slightly better and is the traditional formula; alcohol dries faster, smells less, and is safer to have around other cleaning products. Choose alcohol-based for indoor work, homes with children or pets, and anyone sensitive to fumes. The rule that overrides everything: never let ammonia meet bleach, and never put either one on a coated screen or a tinted window.
What is actually in glass cleaner
Most commercial glass cleaners are mostly water with a small amount of solvent and a surfactant.
Ammonia-based formulas use ammonium hydroxide, an alkaline solvent that cuts greasy and oily films well. This is the classic blue window cleaner chemistry.
Alcohol-based formulas use isopropyl alcohol, ethanol, or a glycol ether. They evaporate quickly and leave little residue.
Many products contain both, and a fair number contain neither, relying on surfactants alone.
The performance gap between them is smaller than most people assume. Technique and the cloth matter more than the bottle.
Source: Household cleaning product formulation references
Which glass cleaner is better, ammonia or alcohol?
Alcohol-based, for most homes. It performs nearly as well, dries faster, has far less odor, and does not carry the serious risk of accidental mixing with bleach. Ammonia-based has a small edge on heavy greasy film, which mainly matters in kitchens.
The safety issue that decides it
Ammonia and chlorine bleach produce chloramine gas when combined. This is a genuine and common household accident, and it causes coughing, chest pain, shortness of breath, and in serious exposures, chemical injury to the lungs.
It happens for a predictable reason. Someone cleans a bathroom with a bleach-based product, then reaches for a glass cleaner to do the mirror, and the two meet in a sink or on a wet surface. Or they mix an unlabeled bottle. The mechanism is in why bleach and ammonia make toxic gas.
Urine also contains ammonia. Using bleach on a pet accident or around a toilet is another way this reaction occurs, and it happens in exactly the small, poorly ventilated room where it is most dangerous.
If it happens: leave the area immediately, get fresh air, and call poison control or emergency services. Do not go back in to open a window.
Because most bathroom cleaners are bleach-based, an ammonia-free glass cleaner removes a whole category of household risk at essentially no cost in performance. That is the strongest argument in this comparison.
Where ammonia is genuinely better
Heavy greasy film. Kitchen windows near a cooktop, and glass that has accumulated cooking residue.
Sticky residue. Ammonia is a stronger solvent on some films.
Cost. Ammonia-based formulas tend to be cheap.
Cold weather. Some ammonia formulas remain effective at lower temperatures than water-heavy alternatives.
Its drawbacks: a sharp odor that irritates airways in a small room, a serious mixing hazard, and a longer list of surfaces it damages.
Where alcohol is genuinely better
Speed of drying. Less time for streaks to form, which is the whole difficulty with glass.
Odor. Much milder, which matters in a bathroom or a car.
Safety around other products. No chloramine risk. Note that alcohol and bleach also must never be combined, since that produces chloroform -- but alcohol-based glass cleaners are typically dilute, and the ammonia-bleach combination is the far more common household accident.
Cold weather glass. Alcohol lowers the freezing point of the solution.
Homes with children, pets, or respiratory sensitivity. Lower fume load in enclosed spaces.
Its drawbacks: flammability in concentrated form, though household glass cleaners are dilute enough that this is a minor concern; and it can damage some plastics and finishes.
Surfaces neither one should touch
This list matters more than the ammonia-versus-alcohol question.
Coated screens and displays. Televisions, monitors, phones, tablets, and laptop screens carry anti-glare and oleophobic coatings that both ammonia and alcohol can strip. The damage is permanent and shows as cloudy patches. Use a dry or barely damp microfiber cloth, or what the device manual specifies -- see can you use glass cleaner on screens and will ammonia damage a TV screen.
Tinted windows. Aftermarket window film is damaged by ammonia, which causes bubbling, discoloration, and lifting. Car window tint and residential film both. Use an ammonia-free product, and check the film manufacturer's guidance.
Acrylic and polycarbonate. Ammonia crazes acrylic, and alcohol clouds some plastics. Storm windows, skylights, and picture frame glazing are often plastic rather than glass.
Eyeglass lenses. Coatings are stripped by both. Use lens cleaner.
Natural stone. Ammonia is alkaline and degrades stone sealer. Alcohol can also affect it.
Painted and finished wood. Ammonia can strip finish, and alcohol dissolves shellac. Overspray onto a window frame does real damage over time.
Leaded and antique glass. Ammonia attacks the lead came in leaded windows.
Technique matters more than the formula
Most streaking blamed on the cleaner is caused by one of these.
Too much product. A light mist is enough. Excess leaves residue that must be buffed off.
Direct sun. The solution evaporates before you can wipe it, locking residue onto the glass. Work in shade or early in the day.
A softener-treated cloth. Fabric softener coats microfiber and makes it smear. Wash cleaning cloths without it.
Spraying the glass rather than the cloth near frames. Overspray runs down and damages frames, sills, and window film edges.
Circular wiping. Work in one direction on one side and the perpendicular direction on the other, so a streak tells you which face it is on.
The full method is in how to clean windows no streaks, and if you prefer to mix your own, the recipe is in diy streak free glass cleaner recipe.
The verdict, with conditions
Use an alcohol-based or ammonia-free cleaner if you have bleach products in the house, children or pets, tinted windows, respiratory sensitivity, or you simply want to remove a real hazard for no performance cost. This is the right default.
Use an ammonia-based cleaner if you are dealing with heavy greasy kitchen glass and you have removed every bleach product from the room first, with ventilation.
Use neither on any screen or display, tinted or filmed glass, acrylic, eyeglasses, natural stone, or antique leaded glass.
Never combine anything. If a first product did not work, rinse the surface fully with plain water before applying another. Every serious home chemical accident starts with escalation.
FAQ
Is ammonia or alcohol better for cleaning windows?
Alcohol-based is the better default for most homes. It performs nearly as well, dries faster, smells much less, and eliminates the risk of accidental mixing with bleach. Ammonia has a small edge on heavy greasy film, which mainly matters on kitchen glass.
Why should you use ammonia free glass cleaner?
Because ammonia and chlorine bleach produce chloramine gas, and most bathroom cleaners are bleach-based. The two commonly meet in a sink or on a wet surface without anyone intending to mix them. Ammonia also damages window tint, acrylic, screen coatings, and antique leaded glass.
Can you use glass cleaner on a TV or computer screen?
No. Screens carry anti-glare and oleophobic coatings that both ammonia and alcohol strip, leaving permanent cloudy patches. Use a dry or barely damp microfiber cloth, or a product the device manufacturer specifies, and apply it to the cloth rather than the screen.
Does ammonia damage tinted windows?
Yes. Aftermarket window film degrades under ammonia, which causes bubbling, discoloration, and lifting at the edges. This applies to both car tint and residential film. Use an ammonia-free cleaner and follow the film manufacturer's guidance.
What happens if you mix glass cleaner and bleach?
If the glass cleaner contains ammonia, the combination releases chloramine gas, which causes coughing, chest pain, and shortness of breath, and can cause chemical injury to the lungs. Leave the area immediately, get fresh air, and call poison control or emergency services.
Why do my windows streak no matter what cleaner I use?
Almost always technique. The usual causes are using too much product, working in direct sun so the solution dries before wiping, using a cloth washed with fabric softener, or old residue built up from years of a film-leaving product.
Glass is the surface that shows every shortcut, and it is usually the first thing a visitor notices. If you want it handled properly on a schedule, get a quote or read more about house cleaning services.