YubiKey is a diverse range of multi-protocol security keys sold by Yubico. These keys are designed to enhance online account security and require both the account login credentials (username and password) as well as the physical YubiKey for access, providing an additional layer of security against virtual account takeovers. 

This can be very useful when accessing valuable data online and can be a great way to secure your private data, investments (for example your brokerage or cryptocurrency exchange account) and money.

The YubiKey 5 series is Yubico's most recent YubiKey series and supports FIDO2 as well as a variety of connections, including USB-A, USB-C, Lightning, and NFC. 

The YubiKey 5 series contains models sporting multiple form factors to cater to different use cases, such as keychain-friendly designs or nano-sized keys for constant connection to a device. 

Buy a YubiKey 5

Meanwhile, the YubiKey 4 series of security keys is a legacy series that Yubico doesn’t sell anymore. 

If you already own a YubiKey 4, you might be wondering if upgrading to the YubiKey 5 is worth it or whether you should keep using the YubiKey 4. 

The short answer is that the upgrade is not worth it unless you specifically require FIDO 2 support and / or connectivity via NFC and Lightning.

YubiKey 4 vs. YubiKey 5: What’s the difference?

  YubiKey 4 YubiKey 5 Models YubiKey 4C Nano, YubiKey 4, YubiKey 4C, YubiKey 4 Nano YubiKey 5 NFC, YubiKey 5C NFC, YubiKey 5C, YubiKey 5 Nano, YubiKey 5C Nano, YubiKey 5Ci Connectivity* USB-A, USB-C  USB-A, USB-C, NFC, Lightning Security functions WebAuthn, FIDO, U2F, OATH - HOTP (Event), OATH - TOTP (Time), Yubico OTP, OpenPGP WebAuthn, FIDO2, U2F, PIV (Smart Card), Yubico OTP , OATH - HOTP (Event), OATH - TOTP (Time), OpenPGP

*Connectivity varies from model to model

As you can see, there isn’t much of a difference between YubiKey 4 and YubiKey 5 series devices – the most important difference by far is that YubiKey 5 devices support the FIDO2 authentication protocol, while YubiKey 4 devices are limited to FIDO U2F.

In addition, certain YubiKey 5 models have connectivity via NFC or Lightning, which can’t be found in the YubiKey 4 range of security keys. 

Beyond these differences, YubiKey 4 and YubiKey 5 series security keys are almost identical. They support the same cryptographic algorithms such as RSA 2048, RSA 4096, ECC p256 and ECC p384.

Both devices are the same when it comes to storage, as YubiKey 4 and YubiKey 5 series can both be used to store up to 32 OATH-TOTP credentials.

YubiKey 4 vs. YubiKey 5: Is the upgrade worth it?

To sum it up, upgrading from a YubiKey 4 to a YubiKey 5 is only worth it if you require FIDO2 support, or you could make use of NFC or Lightning connectivity. If these features are not relevant for you, the upgrade is not worth it as the two series are otherwise almost identical in terms of functionality.

If you’re unsure about which security key is right for you, make sure to also consider some YubiKey alternatives to get a better understanding of what kinds of security keys are available on the market.

What’s the difference between U2F and FIDO2?

FIDO2 is an evolution of the U2F standard aimed at enabling passwordless logins. While both standards offer robust security, FIDO2 adds WebAuthn and CTAP protocols, supporting cross-platform, passwordless authentication. 

U2F was originally a secondary factor for passwords, while FIDO2 enables both single and multi-factor passwordless authentication, offering a smoother and safer user experience overall.

The bottom line

FIDO2 support is a clear advantage the YubiKey 5 series of security keys has over the YubiKey 4 series. In addition, there are YubiKey 5 models that support connectivity via NFC and/or Lightning, which are two types of connections that the YubiKey 4 series lacks.

If you’ve decided to upgrade to the YubiKey 5 series and aren’t sure which model is the right choice for you, we provide a YubiKey 5 vs. YubiKey 5 FIPS comparison.