TOTP vs. OTP vs. HOTP: What are they and which is most secure?

Even when used correctly, strong, random, and unique passwords aren’t foolproof. They can still be hacked, shared unsafely, or forgotten. All of these issues lead to compromised or lost accounts, jeopardizing your company’s important data. 

This is why multi-factor authentication (MFA) has become standard practice for most companies. Unfortunately, not all MFA methods are equally secure. That’s where one-time passwords (OTP), HMAC-based one-time passwords (HOTP), and time-based one-time passwords (TOTP) come in. TOTP represents the current gold standard for MFA, ensuring your accounts remain safe and accessible, even when passwords fail. 

TeamPassword features an integrated TOTP authenticator, so teams can share accounts protected by MFA. 

What are OTP, HOTP, and TOTP?

OTP stands for one-time password—a code you use once and never again. It’s a simple but powerful tool to keep accounts secure when used as an additional layer of authentication on top of your username and password.

Within this category, HOTP and TOTP are two specific ways these codes are created. HOTP uses a counter that increases with each use, while TOTP is based on the current time, refreshing every few seconds. Both aim to prevent unauthorized access, but they take different paths to get there.

What is OTP?

A One-Time Password (OTP) is a unique code used for authentication that is valid for only one login session or transaction. It helps enhance security by preventing reuse and reducing the risk of replay attacks. 

OTPs can be generated and sent via SMS, email, or generated through an app or device. They are often used in MFA systems to verify a user’s identity. OTPs are the broad category under which both HOTP and TOTP fall. Since basic OTP systems rely on SMS and email, they are vulnerable to certain scams, such as smishing.

What is HOTP?

HOTP is a type of OTP that uses a hash-based message authentication code (HMAC) and a counter to generate passwords. Each time the user authenticates, the counter increases, ensuring that every password is unique. 

Because HOTP is event-based, the OTP does not expire until it is used, making it suitable for asynchronous environments. It relies on both the server and client maintaining the same counter value to stay in sync. HOTP is defined in Request for Comments (RFC) 4226 and was one of the first standardized OTP methods.

What is TOTP?

TOTP builds on HOTP by adding a time component to generate one-time passwords. Instead of using a counter, TOTP generates a new password based on the current time and a shared secret key. 

Typically, the OTP changes every 30 seconds, making it valid for only a short window. TOTP is widely used in apps like Google Authenticator as well as integrated into the TeamPassword password manager, and it is more resistant to certain types of attacks compared to HOTP. It is defined in RFC 6238 by Internet Engineering Task Force (IETF) and is a key part of many modern 2FA systems.

How are TOTP, OTP, and HOTP different?

Not all one-time passwords are built the same. While “OTP” is often tossed around as a single concept, it actually branches into different mechanisms—most notably TOTP and HOTP—that determine how the passwords behave and expire.

The difference comes down to time versus events. TOTP is based on a shared clock, generating a fresh code every 30 seconds, while HOTP waits for user action, ticking forward only when triggered. 

Understanding these distinctions is key to choosing the right fit for your security needs:

• TOTP vs OTP: TOTP is a specific type of OTP that generates passwords based on the current time, while OTP is a general term that can refer to any password used once. TOTP adds timed expiration to the OTP concept, increasing security.

• OTP vs HOTP: HOTP is a standardized form of OTP that uses a counter to ensure one-time use. While all HOTP codes are OTP, not all OTP use the HOTP algorithm or its counter-based method.

• TOTP vs HOTP: TOTP passwords expire after a short time window (usually 30 seconds), while HOTP passwords are based on a counter and remain valid until used. TOTP requires time synchronization, whereas HOTP requires counter synchronization.

Here’s a handy summary chart:

Strengths and weaknesses of OTP, TOTP, and HOTP

OTP systems offer a valuable layer of defense against unauthorized access, especially in an era where static credentials are frequently compromised. Whether used as part of MFA or as a standalone validation, OTP systems are designed to limit the damage from stolen or leaked credentials. 

However, the term "OTP" encompasses multiple approaches—including TOTP and HOTP—each with unique properties, limitations, and ideal use cases. Choosing the right one depends on your environment, users, and threat model.

One-time password (OTP)

OTP is a flexible concept that refers to any password that can be used only once. Its biggest advantage lies in reducing the risk of password reuse and credential replay. OTPs are often delivered via SMS or email, or generated through standalone hardware or app-based tokens.

Because they’re easy to implement and require no advanced setup, they’re commonly used in consumer-facing platforms like online banking, e-commerce, and account recovery processes.

However, their security depends heavily on the delivery channel. SMS OTPs, for example, are vulnerable to SIM-swapping and phishing attacks. Email-based OTPs can be intercepted if the user's inbox is compromised. While convenient, these general OTPs should be combined with other security layers (such as device fingerprinting or secure transport protocols) to reduce their exposure to common attack vectors.

Time-based one-time password (TOTP)

TOTP generates codes based on the current time, refreshing every 30 seconds (or a configurable interval). This short validity window makes intercepted codes nearly useless after a brief period, greatly reducing the risk of replay attacks. 

Because the codes are generated locally on the device using a shared secret string of characters, they don’t require an Internet connection once set up—making them suitable for secure mobile apps, enterprise login systems, and VPN access.

That said, TOTP requires the client and server clocks to be closely synchronized. Even small discrepancies can cause login failures if there’s no allowance for time drift. TOTP also doesn’t protect against phishing if the user is tricked into entering a valid code into a malicious site. It works best in real-time, connected environments where time synchronization is reliable—such as cloud platforms, DevOps tools, and corporate SSO systems.

HMAC-based one-time password (HOTP)

HOTP uses a counter to generate each new password, which means a code is only created when the user or system initiates an event—such as pressing a button on a hardware token or starting a login attempt. 

Since it doesn't rely on time, it’s ideal for environments where real-time connectivity is limited or where users may authenticate infrequently. It’s often used in secure physical access systems, offline authentication scenarios, and government-issued hardware tokens.

The trade-off is that HOTP codes remain valid until used, creating a longer window of opportunity for attackers if a code is intercepted. Additionally, both the client and server must keep counters in sync. 

Otherwise, users may face login errors or be locked out. HOTP is best suited for systems that prioritize reliability over immediacy, or where strict control over user-triggered authentication events is possible.

TeamPassword’s built in TOTP adds security without hassle 

TeamPassword has a built-in TOTP authenticator app. Integrating your TOTP system into your password manager makes it easier to utilize MFA, even when sharing accounts with teammates. 

This is just one of the features that makes TeamPassword the best password manager for teams. By making TOTP simple and convenient, you help eliminate the biggest security risk—employees bypassing adding layers of security because they consider it an unnecessary hassle. 

TeamPassword makes it easy for all team members to use MFA. Don’t believe us? Sign up for a 14-day free trial today and try for yourself.