UI/UX Documentation and Summary of current User Studies

Process of an user-friendly product development

The integration of usability into product development is a crucial factor for the success of a product. For the development of the EUDI Wallet, the perspective of the users was therefore taken into account from the very beginning, so that the target groups of future wallet users receive the best possible user experience. Not only aspects of usability and usable security (the user-friendly implementation of security-related features) were taken into account, but also accessibility.

In order to take usability into account in product development and incorporate user feedback into the design, four process steps based on the user-centered design process [1] were followed: research, conception, design, and evaluation (see Fig. 1). It should be noted that these process steps are iterative. The individual sections are not closed processes in themselves, but are repeated in different phases of product development. This means, for example, that a prototype or click dummy is tested in the evaluation phase and the feedback is implemented in a new click dummy, which is then tested again with users.

Fig 1: Process steps for an user-friendly product development

In the first phase, research, a deep understanding of the target group is developed. Methods such as surveys, interviews, and observations are used for this purpose.

During the conception phase, creative solutions are developed for the identified user problems. The ideas are fleshed out using sketches and wireframes, with a focus on content and information design. The user perspective is also continuously evaluated during this phase so that adjustments can be made if necessary.

During the design phase, the designs are refined by creating models. These range from low-fidelity to high-fidelity prototypes. These prototypes serve as a means of communication and are tested to obtain early user feedback on usability.

The final phase is evaluation. After each evaluation, the findings are fed back into the previous phases to ensure continuous improvement. If the tests of a design (e.g., click dummy) are successful, the final implementation of the product begins.

Ensuring accessibility

In product development, it is equally crucial to consider accessibility as an integral part of user-friendliness. Standards such as the WCAG (Web Content Accessibility Guidelines) [2] and ISO 9241-171 [3], which specifically addresses the accessibility of interactive systems, are taken into account. However, it is not enough to simply meet the specified criteria. Rather, active efforts must be made to ensure that usability is achieved for accessibility. This includes, for example, intuitive navigation, understandable content, and alternative input methods.

Discussions have been held with representatives of associations in order to incorporate their feedback into the product design. In addition, user studies with people with different disabilities are planned for the future in order to gather valuable feedback and continuously improve the user experience. This holistic approach is intended to ensure that the product is accessible and user-friendly for everyone.

Application of the process

The EUDI Wallet was able to build on existing research results from previously conducted projects, such as the showcase project “Secure Digital Identities.” This made it possible to move directly to the conception phase at the wireframe level.

Before moving on to the design phase, user studies were conducted at the wireframe level (see Fig. 2) in order to incorporate feedback from the user perspective into the next phase.

In addition, expert reviews were also carried out, taking into account ISO standards and heuristics. These include ISO 9241 [4], which describes user-oriented development processes with a focus on usability and user experience. Important steps are:

1. Understanding the context of use
2. Specifying usage requirements
3. Developing design solutions
4. Evaluate from the user's perspective

Fig 2: Wireframes from the creation of the digital ID card

This includes, for example, ISO Standard 9241-110 [6], which defines principles for dialog design, including criteria such as task suitability and error tolerance.

During each iteration of the screen design process, care was taken to ensure that the architectural concept, security requirements, and UI and UX were aligned to prevent the design of any user flows that would violate the current architectural concept or security standards. The goal is to combine usability and security. Security measures should not be perceived as disruptive or complex, but as a seamless part of the user experience. This should also increase users' security awareness.

Procedure of the user studies

A total of nine user studies have been conducted in the project to date. All user studies followed the same procedure.

The participants for the study were recruited and received an expense allowance. A usability study was conducted in person with the participants, with an average of 1 hour per person scheduled. During recruitment, care was taken to ensure that there was an equal distribution of age and gender in order to obtain the widest possible range of participants. The user studies have so far been conducted exclusively with German participants.

For the purposes of the usability study, participants were asked to complete a questionnaire to assess their own level of technical affinity. This was followed by general questions about their prior knowledge on eIDs, digital identities, and wallets. Participants then had the opportunity to interact with the wallet themselves using a click dummy. During this process, participants were asked to comment aloud on their thoughts while completing various tasks that had to be performed with the click dummy. This made it possible not only to observe their interaction with the dummy, but also to follow their thoughts about the app itself. This made it possible to capture aspects such as:

• Where did they have unanswered questions?
• What information was confusing to them?
• Which interaction steps were unclear?
• etc.

Evaluated features

The tasks that participants in the usability study were asked to complete with the wallet dummy had a different focus for each study. This focus was based on feedback that was important for the current stage of development in order to determine appropriate responses.

The following wallet functions, among others, were evaluated:

App Onboarding

The purpose of app onboarding is to educate users about the wallet's features. It should explain what a wallet is, what credentials can be stored in it, and where and how they can be used. In addition, it should emphasize user awareness of aspects such as security and privacy.

PID (personal identifiable data) Issuance

PID Issuance describes the function that allows users to securely store their ID cards on their smartphones. To do so, they must have an activated online ID function and a German ID card or residence permit. In addition, a 6-digit card PIN must be set.

If this has not yet been set, users can set it themselves in the wallet using their PIN letter and the transport PIN provided therein. Once a 6-digit card PIN is present, the user must enter it and scan the ID card using their smartphone via the NFC interface. A Wallet-PIN must then be set, which the user can use to identify themselves with their digital ID card in the future. After successful issuance, the user will see the digital ID card in their wallet.

PID Inspection

Inspection allows users to view details about their stored credentials or digital ID card. This may include stored attributes, for example, but also who issued the credential and its validity.

PID Presentation

Presentation is the functionality of presenting the digital ID or a credential to a relying party. To present the digital ID for example, the user simply needs to enter their Wallet-PIN to approve the requested data request.

Dashboard (Activity List or History)

Using the dashboard, which can be thought of as an overview of activities already performed, users can view the actions they have carried out with their wallet.

Number of user studies conducted

The user studies focused primarily on the functional flow within the wallet and were conducted using a click dummy of the app rather than the implemented wallet, as this allowed for quick adjustments to be made to the user flow based on user feedback.

The focus was less on design or decisions about colors, fonts, etc. The current priority is on interaction with the ID card for the issuance and presentation of the digital ID card. The following questions, among others, should be clarified:

• Does the user understand that the ID card must be held directly against the smartphone?
• Does the user understand what a transport PIN is and where it can be found?
• Does the user understand what a card PIN is and how it can be set if it has not yet been set?
• Does the user understand the difference between a Wallet-PIN and a Card-PIN (for the ID card)?
• Does the user understand that the Wallet-PIN and not the Card-PIN must be used for presentation?
• Does the user understand where activities carried out with the wallet can be found within the app?
• etc

It should be noted that development is still ongoing, and therefore changes will still be made to the screens. The status presented here is only the current status and should not be considered final.

In summary, a total of nine user studies have been conducted to date in October 2025. The table below (see Table 1) provides a rough overview of the key figures from the user studies conducted.

Criterion	Number
Number of studies conducted	09
Total number of people surveyed	74
Average number of people surveyed per user study	08
Number of people who identified themselves as women	33
Number of people who identified themselves as men	41
Number of digital natives	53
Number of digital immigrants	19
Number of digital outsiders	02

Table 1: Overview of the user studies

Insight into selected feedback from user studies

Exemplary screenshots will be used to illustrate the findings obtained from user studies. These studies focused on interactions and comprehensibility, but not on the design of the wallet itself.

Example 1

Before	Afterwards with feedback from the user studies

Fig 3: Entering the ID Card PIN (screen before and after the user studies)

On this screen, the user is asked to enter the PIN for their ID card.

Users had indicated in the study that they wanted to have control when entering their PIN. Instead of confirming the PIN entry with the last digit, the last digit entered should be deliberately confirmed by pressing an additional button (see Fig. 3 “next button” on the right-hand side). It was also noted that the PIN entry should be made visible (see eye icon on the right-hand side).

The reason for this was that the process was too fast, and users wanted to be sure that they were entering the PIN correctly, as they suspected that repeated incorrect entries would make it more difficult to recover the ID PIN.

Furthermore, the terminology was clarified as an improvement. On the one hand, it was observed that users perceive it as helpful when the length of the PIN (see Fig. 3 - 6-digits on the right-hand side) is emphasized again to better distinguish it from the 5-digit transport PIN. On the other hand, the terminology used by the authorities was adopted, which in turn refers more to the physical document and thus provides a better distinction for the Wallet-PIN for the digital ID card.

Finally, it was observed that some users got confused at this step (see Fig. 3. on the left-hand side) and tried to enter a 5-digit PIN. To help them, another button was added (see Fig. 3. on the right-hand side), which guides them through the process of setting a 6-digit PIN themselves using the 5-digit PIN.

Example 2

Before	Afterwards with feedback from the user studies

Fig 4: Setup of the Wallet-PIN (screen before and after the user studies)

On this screen, the user is asked to set the PIN that will be used to verify their digital ID online.

During user studies, it was observed that there were significant problems with the terminology. Although the wording “security PIN” (see Fig. 4 on the left-hand side) was intended to emphasize its importance, users were unable to distinguish between the Card-PIN for the physical ID and the PIN for the digital ID. Therefore, the terminology was changed to Wallet-PIN (see Fig. 4 on the right-hand side), which greatly improved the comprehensibility and differentiation of the two PINs, as the wording wallet immediately gave users a reference to the app.

In addition, it was observed that users often commented that they wanted to replace the Wallet-PIN with biometric means. Since this change is not possible for security reasons, and users are not desperately looking for a way to change it, they were directly informed that it is not possible to change from a PIN to biometric means (see Fig. 4 on the right-hand side).

Furthermore, it turned out that because participants understood they could not replace the PIN with biometric means, they gave more thought to their Wallet-PIN and chose it carefully, knowing they would have to remember it.

Example 3

Before

Fig 5: Scanning of the ID Card (screen before the user studies)

On this screen, the user is asked to scan their ID card using the NFC interface.

There were frequent problems with users not realizing that scanning had to be activated (see “start scan” button in Fig. 5) and already trying to scan the card and then being confused as to why nothing was happening.

Furthermore, users did not understand that the physical ID card and the smartphone needed to be in direct contact with each other. The scanning instruction was often interpreted to mean that a distance between the card and the smartphone was necessary, which in turn meant that the scan was unsuccessful (see Fig. 5).

Afterwards with feedback from the user studies	NFC Scanning

Fig 6: Scanning of the ID Card (after the user studies) and NFC scanning

The adjustments that were made were therefore, on the one hand, that the scan function was activated immediately upon entering the screen for scanning the card (see Fig. 6 on the left-hand side). Behind the “Ready to Scan” banner, an animation was now displayed, which showed users directly that the card must be placed either at the top of the back of the smartphone (for iPhone models) or in the center of the back of the smartphone (for certain Android models) (see Fig. 6 on the right-hand side).

The animation and the process for starting the scan immediately contributed significantly to the success rate of NFC scanning.

It should be noted that it is currently pending which adjustments need to be made to ensure that scanning the physical ID card is also accessible. These investigations are planned and will be incorporated into the NFC interaction accordingly.

References

[1] C. Abras, D. Maloney-Krichmar, and J. Preece, “User-centered design,” Thousand Oaks: Sage Publications, 2004.

[2] W. W. A. Initiative (WAI), “WCAG 2 Overview,” Web Accessibility Initiative (WAI). Accessed: Nov. 02, 2025. [Online]. Available: https://www.w3.org/WAI/standards-guidelines/wcag/

[3] “ISO 9241-171:2008(en), Ergonomics of human-system interaction — Part 171: Guidance on software accessibility.” Accessed: Nov. 02, 2025. [Online]. Available: https://www.iso.org/obp/ui/#iso:std:iso:9241:-171:ed-1:v1:en

[4] “Digital Technologies | Secure Digital Identities.” Accessed: Nov. 02, 2025. [Online]. Available: https://www.digitale-technologien.de/DT/Navigation/EN/Foerderaufrufe/Archiv/Sichere_Digitale_Identitaeten/sichere_digitale_identitaeten.html

[5] “ISO/TR 9241-100:2023(en), Ergonomics of human-system interaction — Part 100: Overview of ISO 9241 software ergonomic standards.” Accessed: Nov. 02, 2025. [Online]. Available: https://www.iso.org/obp/ui/#iso:std:iso:tr:9241:-100:ed-2:v1:en

[6] “ISO 9241-110:2020(en), Ergonomics of human-system interaction — Part 110: Interaction principles.” Accessed: Nov. 02, 2025. [Online]. Available: https://www.iso.org/obp/ui/en/#iso:std:iso:9241:-110:ed-2:v1:en