I have a Galaxy S21 5G and I'm looking at the Galaxy A57 5G

The month Samsung's promise of security updates for this phone runs until: the date Samsung's own page gives, or worked out from the number of years Samsung announced, counted from when the phone came out.

A phone bought later or used has fewer years left. "No longer updated" means the phone is no longer on Samsung's list of phones that get security updates.

Matters most if: You plan to keep the phone for years, or you're buying one used.

How many new versions of Android (with the matching One UI) Samsung promised this phone would get after the one it came with.

Samsung promises a number of versions rather than a date. Each upgrade brings new features; security updates are a separate promise, in the row above.

Matters most if: You want the newest Android features for years to come.

The version of Android, Google's phone software, that was installed when the phone first came out. Samsung adds its own design and features on top, called One UI (TouchWiz on older phones).

A Galaxy moves to newer Android versions through updates, so this shows where it started, not what it runs today.

Galaxy AI is Samsung's name for its set of AI features, such as live translation of phone calls, writing help and photo editing that fills in parts of a picture.

Samsung lists which phones get Galaxy AI, at launch or through a One UI update. Some features work on the phone itself and others use the internet; Samsung lists which is which, and availability varies by language and country.

Matters most if: You want AI features such as call translation or photo editing built into the phone.

What Samsung charged in the US when the phone launched, for the version with the least storage, before sales tax. Phones from before about 2014 were often priced with a two-year carrier contract.

This is not what it costs today: check the used and refurbished links for current prices. If Samsung has not confirmed a price, the site shows "Price not confirmed by Samsung".

How much charge the battery holds, measured in mAh (milliamp-hours). Samsung lists a typical figure; we show the one Samsung gives.

A bigger number stores more energy, but how long a charge lasts also depends on the screen, the chip and which features you use.

Samsung's own figure for how long a full charge lasts in one of its tests, usually hours of video playback (talk time on older phones).

It is a lab test of one activity, so real use with a mix of apps is usually shorter. Compare it only with another Samsung figure for the same test.

Matters most if: You are often away from a charger all day.

The resolution of the main camera's sensor in megapixels (MP), meaning millions of light-catching dots.

High-megapixel cameras usually combine neighboring dots into a smaller photo by default; you can switch to full resolution for large prints or cropping.

Matters most if: You want full-size photos for large prints or for cropping later.

The resolution in megapixels (MP) of the telephoto camera: a separate zoom lens that sees far-away things as if you were closer. "None" means the phone has no telephoto camera. Some Ultra models have two.

At the telephoto's own zoom level, the photo comes from a real lens instead of a cropped, enlarged image.

Matters most if: You photograph kids' sports, concerts, pets or wildlife from a distance.

How far the telephoto lens zooms on its own compared with the main camera (1x), for example '3x optical zoom'. Where Samsung lists two telephoto lenses, the comparison uses the longer one.

At this level the lens does the zooming, so no part of the image is cut away. 'Optical quality zoom' figures some models list come from cropping a high-resolution camera, not from a lens.

Matters most if: You compare zoom between phones: compare this row, not the 'up to' figures.

The farthest the camera can zoom, with software doing the work beyond what the lenses reach. Samsung calls it Space Zoom on many models.

Past the lens's own zoom, the camera enlarges part of the picture and relies on processing to keep it sharp, so the highest levels lose detail.

Matters most if: You zoom far and need the photo to show fine details.

More in the glossary →

The resolution in megapixels (MP) of the selfie camera on the front.

A higher number keeps more detail in selfies and video calls, but light and processing matter as much.

The highest video quality the rear camera records. 4K and 8K describe the picture size (8K is larger), and fps (frames per second) is how many still images make up each second.

Higher settings make bigger files, so long 8K or 4K 60 fps clips fill storage quickly.

Matters most if: You film a lot.

The screen size, measured corner to corner (diagonally) in inches. 1 inch is 25.4 mm.

Samsung measures the screen as a full rectangle, so with rounded corners the visible area is a little smaller.

The type of screen, in Samsung's own words, such as Super AMOLED or Dynamic AMOLED 2X. AMOLED screens light each dot on its own, so black areas are truly black.

The name alone does not tell you how bright or sharp a screen is, so compare the brightness, resolution and refresh rate rows.

The range of refresh rates the screen moves between on its own, in Samsung's words, such as '1~120Hz'. A screen that can slow to 1 Hz saves battery on still images.

The screen speeds up for scrolling and games and slows down for reading, to balance smoothness and battery life.

Matters most if: You care about battery life as well as smooth scrolling.

The brightest the screen can get, in nits (a unit of screen brightness; higher is brighter), as Samsung measures it.

A high peak brightness makes the screen easier to see in direct sunlight. Makers measure peak brightness in different ways, so compare it only between phones from the same maker.

Matters most if: You use your phone outdoors a lot, such as for maps or photos in sunlight.

Ways to unlock the phone with your body instead of typing a PIN: a fingerprint sensor (in the screen, the side key, the home key or on the back), face recognition, or on some older models an iris scanner.

An ultrasonic sensor in the screen reads your finger with sound waves; others use light. Where the sensor sits changes how you unlock the phone with one hand.

How much the phone weighs in grams (g); about 28 g is 1 ounce.

You feel the weight most when you hold the phone up for a long time, such as reading or filming.

The phone's size in millimeters (mm): height x width x depth (thickness). 25.4 mm is 1 inch.

Height and width tell you whether it fits your pocket and hand; depth is how thick it is.

What the outside of the phone is made of: the cover glass over the screen and back, and the frame around the edge, as Samsung lists them.

Glass names such as Corning Gorilla Glass Victus or Gorilla Armor are tougher generations of glass; a titanium or aluminum frame changes the weight and feel more than the strength in daily use.

The kind of USB port Samsung lists: Micro USB on older phones, USB-C on newer ones, with a USB version such as USB 2.0 or USB 3.2. It concerns moving data over a cable, such as copying files to a computer.

A higher USB version can copy files faster with a cable that supports it. Charging speed is listed separately.

How fast the phone charges with a cable, in Samsung's words, such as Super Fast Charging (25W or 45W). W (watts) is how much power the charger can deliver.

The top speed needs a charger and cable that support it; recent Galaxy phones come with a cable but no charger.

Matters most if: You often need a quick top-up before heading out.

Whether and how fast the phone charges on a wireless charging pad, in Samsung's words, such as Fast Wireless Charging 2.0.

The fastest speed usually needs a matching Samsung charger. Wireless charging is slower than a cable but saves plugging in.

Wireless PowerShare lets the phone wirelessly charge another device, such as Galaxy Buds or a Galaxy Watch, placed on its back.

It works with devices that charge wirelessly, and it uses the phone's own battery.

Matters most if: You carry wireless earbuds or a watch and want to top them up away from a charger.

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The Wi-Fi generation, such as Wi-Fi 5, Wi-Fi 6E or Wi-Fi 7. 6E and 7 can also use the 6 GHz band, which is less crowded. Older phones list only the 802.11 letters (n is Wi-Fi 4, ac is Wi-Fi 5, ax is Wi-Fi 6).

A newer generation helps only with a router that supports it, and the 6 GHz band is not allowed in every country.

Matters most if: You have, or plan to buy, a Wi-Fi 6E or Wi-Fi 7 router.

Bluetooth connects wireless accessories, such as earbuds and watches, to the phone. The number, such as v5.3, is the Bluetooth version.

Newer versions add features such as LE Audio, but your earbuds or watch need to support them too.

Ultra-Wideband (UWB) is a radio chip that measures how far away another UWB device is and in which direction. It only works with another device that also has UWB.

With a tracker tag that has UWB, such as a Galaxy SmartTag+, the phone can show distance and direction to find keys or a bag.

Matters most if: You use tracker tags to find keys or bags.

mmWave ("millimeter wave") is a high-band type of 5G. The more common type, Sub-6, uses frequencies below 6 GHz. Usually only the US versions of Galaxy phones can use mmWave.

You need a carrier with mmWave 5G where you use the phone; the carrier's network decides which type the phone uses.

Matters most if: Your carrier offers mmWave 5G where you live or work.

Which SIM the phone takes: a SIM card from your carrier in a tray (nano SIM), an eSIM (a digital SIM built into the phone), or both. Samsung lists the combinations, such as "SIM 1 + eSIM".

Whether you can use eSIM depends on your carrier and country. Some versions of a model take two SIM cards, others one SIM card and an eSIM.

Matters most if: You travel abroad or want two phone lines on one phone.

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The main processor: the part that runs apps, camera processing and on-device AI. Samsung uses its own Exynos chips in some countries and Qualcomm Snapdragon chips in others, sometimes for the same model.

Where the chip depends on the country, the page shows a switch for the versions Samsung lists. A newer phone can have an older chip, so compare the chip names rather than the year.

Matters most if: You are buying a model that was sold with two different chips.

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A separate secure processor that keeps passwords, PINs and other sensitive data apart from the rest of the phone. Samsung calls it Knox Vault.

Phones where Samsung names no security processor still have Samsung Knox security in their software; this row only shows a separate chip Samsung names.

More in the glossary →

How much space the phone has for apps, photos, videos and files, in GB (gigabytes) or TB (terabytes; 1 TB is 1,000 GB).

Each storage size is sold at its own price, and not every size is sold in every country. You get less usable space than the number shown, because some of it holds the phone's own software.