Our results show that there is no overarching design
pattern for the user journey that most websites follow. Instead,
we found the design space to be clustered into groups of
websites with very similar patterns, some of those favored by
the top websites and others by less popular sites. The only
design aspects that almost all websites agree on about 2FA
are that it is an optional feature, how it should be called
and described, and where it should be found in the account
settings. In contrast, for the crucial steps of setting up and
using 2FA, we found that websites implement mixed strategies,
such as varying numbers of simultaneously supported 2FA
technologies, inconsistent presentation of device remembrance
options, or varying degrees of feedback to users.
According to UX guidelines, this lack of consistency in-
creases users’ cognitive load and should be avoided. However,
consistency alone does not guarantee a good user experience.
We found that several of the more consistently used design pat-
terns have been described in prior work as problematic for user
experience, including non-encouraging descriptions or missing
possibilities to personalize the 2FA. We also discovered that the
journeys of top websites, like icloud.com, are outliers from
the best practices in the academic literature. Therefore, our
results create a call for action to reinvestigate what constitutes
a good overall 2FA user experience, to study whether there
is a “gold standard” for implementing 2FA user journeys, or
to explore the motivations of website developers to implement
specific design patterns.
II. BACKGROUND
A. Two-Factor Authentication
With two-factor authentication enabled on a website, a user
must successfully provide two authentication factors to verify
their identity. Almost always, the first factor is a traditional
text-based password. For the second factor, there are different
technical realizations of knowledge, possession, and inherence
factors. Most common [5], [12] are one-time codes delivered
via SMS text-message, phone call, or TOTP [53] apps, like
Google Authenticator, Duo, or custom apps that the user
registered with the website; push notifications by sending an
alert message to a dedicated app on the user’s phone that asks
the user to confirm a login attempt; and hardware tokens via
the U2F or FIDO2/WebAuthn [82] standards that rely on public
key cryptography and challenge-response protocols.
Each of these comes with its own set of usability and
security benefits and drawbacks [63]. Important for our work
is that a website with 2FA support can offer one or multiple of
those 2FA options, may even allow users to set one of those
solutions up multiple times, or may enforce a particular order
in which they can be set up or used.
A commonly acknowledged problem with two-factor au-
thentication is account recovery when a user loses access to a
factor (e.g., a mobile device with the TOTP app is unavailable).
Often the strategy to avoid lockout from a 2FA-protected
account is to set up a dedicated recovery option, such as
printed-out one-time passwords that can replace another 2FA
option, or to configure multiple 2FA options, when supported
by the website, e.g., multiple hardware security keys.
B. User Experience
Unfortunately, providing an exact definition of “user ex-
perience” is very difficult, as there is no consensus on the
exact definition [8], [40], [46], [59]. However, a common topic
among the definitions is that UX encompasses the various
aspects of user interaction with a product, such as a website.
Cooper et al. [16] note that there exist three overlapping
concerns for UX: form, content, and behavior. While form
and content (e.g., UI design or phrasing) have an impact on
usability, this work focuses on behavior (i.e., functionality) and
only touches on some aspects of form and content.
To help designers provide the best possible user experi-
ence, various best practices and general guidelines have been
developed (e.g., books [16], [43], [70], [77], [84] or online re-
sources, such as Laws of UX [83], Nielsen Norman Group [3],
or Interaction Design Foundation [2]). Among the earliest are
Shneiderman’s eight "Golden Rules" for interface design [69],
[70] and Nielsen’s "10 Usability Heuristics for User Interface
Design" [55], [58]. Shneiderman’s rules state, for instance,
that one should strive for consistency and provide informative
feedback to users. Of Nielsen’s heuristics, heuristic nr. 4, also
known as Jakob’s law of Internet user experience [57], is the
most important for this work and provides the motivation to
study the consistency of 2FA user journeys across websites.
This heuristic states that “users spend most of their time on
other sites” and that “users prefer a site to work the same way
as all the other sites they already know.” As a consequence, one
should “design for patterns for which users are accustomed.”
Having such conventions and consistency helps users build
upon existing mental models and avoid cognitive friction by
forcing them to learn something new [84]. If an unconventional
website mismatches the user’s mental model, the website will
be difficult to learn, difficult to use, or even rejected [77]. One
way to drive external consistency is to make ample use of
guidelines. For instance, for apps there exist Google’s Mate-
rial Design Guidelines [36] and Apple’s Human Interaction
Guidelines [9]. We are not aware of any general guidelines
for implementers and designers of two-factor authentication
on websites, although there are case-specific guidelines (for
example, FIDO2 [29]) or small collections of best practices
(e.g., [23], [75]).
Although in this work we focus on external, functional
consistency, some of the comparison factors for 2FA user
journeys that we identified (see Section VI) also touch on other
UX guidelines and best practices. Tesler’s law [84] states that
for any system there is a certain amount of complexity that
cannot be reduced, and it is recommended that the product
design ensures that as much as possible of the burden on
the user is lifted. Krug [43] recommends that if a difficulty
for the user cannot be avoided, the design should provide
brief and timely guidance, and Cooper et al. [16] recommend
contextual help and assistive interfaces without the need to
break the user’s flow. If it cannot be avoided that the user has
to learn something new, users learn best from examples (e.g.,
pictures, screenshots, or short tutorial videos) [77]. In addition,
Hick’s law [84] recommends breaking down complex tasks
into smaller steps to decrease the cognitive load. Moreover,
excise tasks, such as navigational excise, should be reduced,
e.g., by reducing the number of places that a user must go
and providing clear overviews [16]. Hereby, it is important
2