Airport security and liquids rules: what you can bring

Every liquid, gel, aerosol, cream or paste you carry into the cabin must be in a container of 100 ml (3.4 oz) or less. All of those containers must fit in one clear resealable plastic bag of roughly 1 litre (1 quart) per passenger, and the bag comes out of your hand luggage at the screening lane. Anything bigger goes in your checked bag or gets left behind.

The limit is on the container, not the contents. A 200 ml bottle with 30 ml of shampoo in it is still a 200 ml container and will be refused. Buy travel-size bottles, or decant into small ones before you leave home.

Laptops, tablets and large electronics usually come out of the bag and go in a separate tray. Coats, belts, watches and anything metal go in a tray too. Empty your pockets before you reach the lane, not while the queue watches.

The rules apply to anyone passing through a security checkpoint into a departure area, whatever their nationality, ticket class or frequent-flyer status. There is no exemption for children, though the bag allowance is usually per passenger, so a family of four can carry four bags.

The 100 ml framework is the international baseline set after the 2006 transatlantic liquid bomb plot, and it is written into the rules of the US TSA, the UK Department for Transport, the EU, Canada's CATSA, Australia's Home Affairs and New Zealand's Aviation Security Service. National variations exist in the details: bag dimensions, whether shoes come off, and how strictly the bag is enforced.

Transit passengers are screened again at many airports even when they never leave the terminal. If you buy a large bottle of spirits in a duty-free shop at your origin, it can be taken off you at a transfer in a country that re-screens cabin liquids. Check the transfer airport's rule before you buy.

Start the night before. Sort every liquid you plan to carry into containers of 100 ml or less, then test-fit them in the clear bag with the zip closed. If it will not close, you have too much and something has to move to the checked bag.

At the airport, take the bag out of your hand luggage before you reach the tray stack. Put it in its own tray, on top, where the screener can see it. Laptops and large cameras go in a separate tray, nothing stacked on top. Coats, jackets, belts and metal go in a third tray.

After screening, repack the liquids bag inside your hand luggage rather than leaving it loose. On a tight connection you will not have time to reorganise, and loose bottles are the usual reason a bag gets pulled for a second look.

If you are stopped, stay calm and let the officer finish. You can usually choose to abandon the item, return to check-in to check a bag, or in some airports pay for a courier or locker service. Arguing the size of a bottle rarely changes the outcome.

Screening itself is free. The real costs are the checked-bag fee you pay to move full-size liquids out of the cabin, and the markup on drinks and toiletries bought airside. A checked bag on a low-cost carrier is commonly 20–60 USD equivalent each way on a long-haul route, and a 200 ml bottle of shampoo airside can cost several times the supermarket price.

Time at the lane depends on the airport, the hour and the equipment. At a large hub in peak season, allow 30–45 minutes from joining the queue to clearing the lane; at a small regional airport outside peak hours, 5–10 minutes is normal. Add time if you are travelling with an infant, medication or a group.

The biggest time saver is not the liquid rule but your own preparation: bag out, electronics out, pockets empty, belt off. Travellers who do this clear in a fraction of the time of those who unpack at the tray.

The definition is broader than most people expect. It covers water, juice, perfume, aftershave, lotion, sunscreen, toothpaste, hair gel, lip gloss, mascara, liquid foundation, contact lens solution, shaving foam, deodorant stick in some countries, peanut butter, honey, jam, soft cheese, soup and any food with a sauce. If it spreads, pours, sprays or smears, treat it as a liquid.

Powders are a separate category in the US and some other countries: containers of powder over 350 ml may need to come out of the bag for extra screening. Coffee, spices, protein powder and baby formula powder are the usual examples.

Exemptions exist for things you need for a medical or care reason. Baby milk, formula, sterilised water and baby food are allowed over 100 ml. Prescription and essential over-the-counter medicine is allowed, and insulin, inhalers and epinephrine auto-injectors are treated as essential. Declare them at the start of screening and carry documentation: a prescription copy, the pharmacy label, or a doctor's letter for injectables. You may be asked to taste a drink or open a container.

Duty-free liquids bought after security are sealed in a tamper-evident bag with the receipt inside. Keep the bag sealed until you reach your final destination. At a transfer airport that re-screens cabin baggage, the sealed bag is usually accepted, but not everywhere; a few airports still confiscate it. If your itinerary has a self-transfer or a change of terminal, assume the bottle may not survive.

A growing number of airports have installed computed tomography (CT) cabin baggage scanners. These produce a 3D image, so laptops and large electronics can stay in the bag and, at some airports, the 100 ml container limit and the 1 litre bag have been dropped for the standard lane. The UK, the US, the Netherlands and several other countries have been rolling this out airport by airport rather than country by country.

The practical trap is inconsistency. You can fly out of an airport with CT lanes and land at one without, or transfer through a terminal still using older X-ray machines. The safe habit is to keep packing to the 100 ml rule even when your departure airport no longer requires it, because the return or transfer airport probably does.

Do not assume a CT lane means no rules at all. Some airports keep the bag requirement, some ask for electronics out anyway, and some have CT machines only in certain terminals or only for certain lanes. Follow the signs and the officer's instructions on the day; they override anything you read online, including this page.

Once a bag is checked, the 100 ml rule no longer applies to toiletries, drinks or food. Full-size shampoo, wine, olive oil and jam can travel in the hold, packed so they cannot leak onto your clothes. Wrap bottles in a sealed plastic bag, then in a towel, and put them in the middle of the case.

Some items are banned from the hold entirely. Lithium batteries and power banks must travel in the cabin, e-cigarettes and vaping devices likewise, and spare lithium batteries must be in carry-on. Flammable liquids, fireworks, compressed gas and most aerosols above the airline's limit are prohibited in both cabin and hold. Check the airline's dangerous goods page, not just the airport's security page.

If you are travelling with a firearm, ammunition, a knife or sporting equipment, it must be declared, packed per the airline's rules and usually checked. Never arrive at the security lane with these items expecting to explain them there.

The short answer is 100 ml containers in one clear 1 litre bag per person, with exemptions for baby food and medicine, and duty-free liquids allowed only in a sealed tamper-evident bag.

It applies to every passenger entering a departure area, on every airline and in every cabin class, with the details set by each country's aviation security authority.

It costs nothing at the lane; the money goes on checked bags and airside purchases, and the time is 5–45 minutes depending on the airport and the hour.