How Do Credit Card Readers Work?

How Do Credit Card Readers Work?
How credit card processing machines work.
by Square Jan 08, 2016 — 5 min read
How Do Credit Card Readers Work?

You process transactions with them every day, but do you really know how credit card readers work? What’s actually happening from swipe (or dip, in the case of chip cards) to the completion of a sale? Below, we explain the credit card processing system and take you through how credit card readers work for magstripe cards, chip cards, and contactless payments. Knowing how credit card readers work will make you a much more informed small business owner.

How do credit card readers work?

Credit card readers read a customer’s credit card information and securely communicate the transaction data to the banks and credit card networks. Whether they’re traditional credit card machines or mobile card readers, it’s helpful to understand the credit card processing payment flow—from the moment of swipe or dip to the settlement.

Credit card processing explained

Credit card processing with Square can be broken down into three stages: authorization, capture, and settlement. Let’s go through each:

Step 1: Authorization

When a Square seller swipes or dips a customer’s card, the payment request is sent to Square. We then pass the transaction to a financial institution known as the acquiring bank (sometimes called a merchant bank or acquirer). The acquiring bank acts as a go-between and sends the request to the issuing bank (the customer’s credit card company). The issuing bank checks if the customer has enough money or credit for the charge. The issuing bank also uses fraud detection software to check if the transaction is legitimate. If everything checks out, the transaction is authorized and a hold is put on the funds, which shows up as “pending.”

Step 2: Capture

The funds are then moved from the credit card company to the acquiring bank. Lots of payments are moved across together in one big batch, so this part of the process is sometimes known as batching.

Step 3: Settlement

It’s pay day. The funds from the credit card sale get settled through Square’s systems and are transferred into the seller’s bank account. Square sellers receive their funds in one to two business days. For sellers who would like their funds even faster, Square has two swifter options, each for just one percent of the total transfer amount. Scheduled transfer gives sellers the option to receive the day’s sales in their bank accounts on the same day at a set time, seven days a week. Sellers can also opt for instant transfer, which is a one-off instantaneous transfer of a specific sale into their accounts. This can help immensely should a business have cash flow issues.

How do the actual credit card readers work? Magstripe readers and chip card readers function a bit differently in credit card transactions.

How magstripe credit card readers work

Magstripe-only cards are being phased out and replaced by chip cards. And good riddance, because they are prone to fraud and have extremely outdated technology (the same technology, in fact, as cassette tapes). On magstripe cards, the payment information is on the backside magnetic strip and is static, meaning the info stays the same every time the card is swiped. This makes them vulnerable to credit card fraud, since the cardholder’s info can easily be lifted and cloned using something called a skimmer, which is simple for fraudsters to use and only costs about $20. When you swipe a magnetic-stripe card, the technology transmits the bank info to the card reader, which sends it to Square. We then pass along that information to the acquiring bank.

Square’s magstripe reader plugs into your iOS or Android device’s headset jack so you can take credit card payments anywhere. The reader works with our free POS app and card information is always safe since Square’s advanced security technology encrypts transactions from the moment of swipe.

How chip (EMV) readers work

What is EMV? EMV®, developed and managed by American Express, Discover, JCB, Mastercard, UnionPay, and Visa, is the global standard for chip cards. Chip cards are far more secure than magstripe cards and have been the standard in most of the world for over a decade. Why the switch over to chip cards? The U.S. has the unfortunate distinction of having nearly half the world’s credit card fraud, despite being home to only a quarter of the world’s credit card transactions. Our switch to chip cards is an effort to help curb fraud in this country.

Chip cards are far more secure than magstripe cards because the data on them is dynamically encrypted. This makes it extremely difficult for fraudsters to isolate the cardholder data and extract it into anything meaningful. EMV technology has been proven to help fight fraud. Countries that have already switched to EMV chip cards have seen a dramatic reduction in fraud since phasing out magstripe cards.

In an effort to accelerate the adoption of chip cards in the United States, something called the liability shift happened in October 2015. Under the liability shift, sellers who continue to swipe chip cards could be on the hook for certain kinds of fraud. No one wants that, so it makes sense for sellers to get a card reader that accepts chip cards.

Square’s contactless and chip reader allows you to securely take chip card and NFC (contactless) payments and works in conjunction with our free POS app for iOS and Android. If you purchase a contactless and chip reader, Square covers you for the liability shift until your reader arrives. Have customers without chip cards? Not a problem. The reader comes with a magstripe reader so you can swipe cards without chips.

How do chip card readers work?

Each EMV card has an embedded computer chip that stores cardholders’ bank details. However, unlike magstripe cards, where the payment info is static, chip card data keeps changing, which makes it extremely difficult for fraudsters to extract anything useful. When a chip card is dipped into a chip card reader, the chip and reader communicate with each other in an encrypted language. A new code is created for each transaction and the data is encrypted the moment the card is dipped. The encrypted data is then sent to the acquirer as explained above.

But while chip card payments are extremely secure, the processing time is slower than it is with magstripe cards. (All those security checks make the transaction take longer.) This sluggishness can be particularly irritating if your business is one that typically has long lines to check out. Contactless (NFC) payments, on the other hand, are much (much faster). They’re just as secure as chip cards but much more convenient and are processed in a fraction of the time.

How Apple Pay and Android Pay readers work

NFC stands for “near field communication. NFC (or “contactless”) payments keep your bank info safe with several layers of security. Like chip cards, NFC data is both encrypted and dynamic, which means it changes for every transaction. Apple Pay, Android Pay, and Samsung Pay are all examples of popular NFC payment apps. Contactless payments like Apple Pay have an added level of security because they require a customer’s fingerprint to unlock the app to initiate the payment. And in the unfortunate case that your phone is stolen, a fraudster wouldn’t be able to get past this fingerprint verification step.

To process NFC payments, customers hold their smartphone over the contactless reader, with their finger on the home button. This triggers the transaction, which, as we mentioned, takes just seconds.

Apple Pay uses a technology known as tokenization, which keeps bank info safe. To set up Apple Pay, you take a photo of your credit card within the app. Apple then transmits the card info to your credit card provider. The card provider then swaps out your card info with a “token,” or random series of numbers. The token is sent to Apple, which sends it to your phone. Because the token and not your actual credit card info is transmitted during each payment, your info is safe and fraudsters can’t do anything with the scrambled info that’s transmitted. A different token is also generated for each transaction. All this makes it extremely difficult for a fraudster to hack.

We’re not your typical merchant service provider. Square charges just 2.6% + 10¢ per swipe, dip, or tap, and 3.5% + 15¢ for each manually entered transaction. There are no long-term contracts, hidden fees, or surprises. So no matter how your customers choose to pay, we’ve got you covered.

The Bottom Line is brought to you by a global team of collaborators who believe that anyone should be able to participate and thrive in the economy.


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