Encouraging Sustainable Behaviour on Depop through Digital Nudges

Project goal

Design and prototype digital nudges to encourage sustainable behaviours on Depop, informed by behavioural science and user research.

Research goals

To understand how sustainability influences behaviour on second-hand fashion platforms, I followed a user-centred design approach focused on Generation Z users with experience buying or selling used clothing online — the core user group on Depop.

The goal of this research phase was to explore:

• How sustainability factors into real decision-making

• The gap between users’ values and their in-the-moment behaviour

• Which behavioural cues could influence sustainable actions without restricting choice

To do this, I combined:

• Structured interviews

• A context-of-use survey

• Secondary research into behavioural heuristics and biases

Problem statement

Second-hand fashion platforms like Depop promote sustainability by default, yet user behaviour is still strongly shaped by cognitive biases and interface design.

The challenge was to explore how digital nudges could encourage more sustainable actions without removing user autonomy.

Key research insights

1. Sustainability is valued — but rarely drives behaviour in the moment

Most participants expressed concern about sustainability, particularly around packaging and environmental impact. However, during browsing and purchasing, these considerations were often secondary to convenience, trust, and perceived value.

This revealed a clear gap between what users say matters and what actually influences decisions.

2. Behaviour is shaped by social and psychological cues

Ratings, reviews, popularity, and perceived honesty strongly influenced participants’ decisions. Loss aversion and positive reinforcement were also seen as effective motivators.

These insights suggested that subtle nudges, rather than explicit sustainability messaging, could be more effective in shaping behaviour.

3. Feedback after purchase reinforces positive behaviour

Many participants valued receiving feedback about the sustainability of their purchase after completing a transaction, describing it as motivating and likely to influence future choices.

Context of use & constraints

The context-of-use survey revealed several important patterns:

• Most users primarily use Depop to sell, not buy

• Nearly all access the platform via smartphone

• The mobile app was strongly preferred over the website

• Overall satisfaction with Depop was high

These findings highlighted the importance of designing nudges that integrate seamlessly into existing behaviours rather than introducing friction.

Behavioural insights

Based on primary research and secondary sources, I identified key behavioural biases influencing user decisions:

• Social proof

• Loss aversion

• Default bias

These insights directly informed the design of the digital nudges.

Personas

I created three personas based on interview data, survey responses, and secondary research. They represented typical Depop users and helped synthesise user goals, motivations, and attitudes toward sustainability.

These personas were used throughout the design process to evaluate where and how nudges could be most effective.

User journey maps

User journey maps were used to identify moments of uncertainty and decision-making where digital nudges could be most effective.

From research insights to design opportunities

Research showed that users’ decisions on Depop are shaped more by trust signals, social cues, and perceived effort than by sustainability alone.

Rather than redesigning the platform, I focused on identifying moments in the existing journey where small interventions could meaningfully influence behaviour. These interventions took the form of digital nudges.

In this project, digital nudges refer to subtle interface elements designed to influence behaviour in predictable ways, without restricting user choice. Rather than forcing sustainable actions, the nudges aimed to make certain options more visible, easier, or more reassuring at key moments in the user journey.

Designing within an existing interface

I did not create paper or low-fidelity wireframes for this project. Instead, I worked directly within Depop’s existing website structure, adding and adapting interface elements where nudges could naturally fit.

This approach allowed me to:

• Preserve users’ mental models

• Focus on behavioural influence rather than layout exploration

• Test whether nudges could integrate into a real-world product

With my current experience, I would explore ideas earlier through low-fidelity wireframes and adopt a mobile-first approach. However, working within an established interface helped ground decisions in realistic constraints.

Identifying key intervention points

Based on research and journey mapping, I identified four moments where nudges could have the greatest impact:

• Exploration — forming first impressions

• Search and filtering — evaluating trade-offs

• Post-purchase — reflection and learning

• Profile — reinforcing long-term behaviour

These moments aligned with points where users seek reassurance, assess trust, and are receptive to feedback.

Translating nudges into interface elements

Behavioural insights were translated into concrete design decisions, for example:

• Social norms → highlighting popular sellers and highly rated listings

• Moral norms → trusted seller badges and eco-friendly packaging indicators

• Status quo bias → default search distances encouraging local purchases

• Loss aversion → discounted clothing sections

• Endowment effect → progress-based sustainability badges in user profiles

Each nudge was designed to be:

• Optional and non-intrusive

• Contextual to the user’s goal

• Visually lightweight

The following design interventions show how behavioural insights were translated into subtle, context-aware digital nudges across the Depop experience.

Structuring content with users in mind

To support these interventions, I conducted a card-sorting study to understand how users prioritised homepage content.

While the activity did not determine which nudges were used, it informed their placement and ensured new elements aligned with content users already valued.

Platform and scope

Although most participants primarily used Depop’s mobile app, this project explored nudges through a desktop website prototype, influenced by academic scope and tooling constraints.

This decision is reflected on further in the Going forward section.

Sitemap

The sitemap helped identify where digital nudges could be integrated into Depop’s existing structure without disrupting familiar user flows.

Usability testing

I conducted moderated usability testing to assess whether the proposed nudges were noticeable, understandable, and aligned with user expectations.

Participants were asked to complete exploratory tasks using a high-fidelity interactive desktop prototype developed in Adobe XD. Sessions combined task observation, think-aloud, and follow-up interviews.

The goal was not to validate visual design, but to understand how users perceived and interpreted the nudges.

Key findings

Several nudges were consistently noticed and interpreted as intended:

• Default search distance

Users rarely adjusted the pre-set distance, suggesting the default successfully influenced behaviour with minimal effort.

• Seller ratings, reviews, and trust badges

These elements were clearly understood and associated with credibility, particularly when browsing unfamiliar sellers.

• Post-purchase sustainability feedback

Participants described the feedback as informative and motivating, even when not interacting with additional details.

Usability issues

Testing also revealed areas for improvement:

• Seller ratings were sometimes misinterpreted as product ratings

• Search distance was occasionally associated with in-person collection

• Placeholder content influenced decisions more than interface cues

These findings highlighted how small clarity gaps can affect interpretation, particularly in prototypes with simulated interactions.

Key takeaways

Subtle nudges that aligned with existing user expectations, such as defaults and trust signals, were more effective than those requiring additional explanation.

Testing reinforced the importance of clear microcopy and visual hierarchy when introducing behavioural design elements.

Reflections on scope and platform choice

There was a mismatch between research insights and some design decisions. While most users accessed Depop via mobile and primarily used the platform to sell items, the prototype focused on a desktop purchasing journey.

This was influenced by academic scope and tooling constraints at the time. With my current experience, I would align platform choice more closely with real user behaviour and prioritise mobile-first design.

Design improvements I would make

In a next iteration, I would:

• Clarify distinctions between seller ratings and product information

• Improve microcopy around search distance and delivery expectations

• Replace placeholder content with realistic listings

• Increase interaction depth and feedback within the prototype

What I would do differently today

If approaching this project again, I would:

• Design mobile-first

• Include selling-related journeys alongside purchasing flows

• Prototype earlier using low-fidelity sketches

• Plan multiple testing iterations

Next steps & future work

Future work would focus on iterating the prototype and validating the effectiveness of the nudges at scale, including:

• Quantitative testing to measure behavioural impact

• A/B testing different nudge implementations

• Analytics-driven evaluation of sustainable behaviour adoption

While exploratory, this project provides a strong foundation for further research into ethical, sustainability-focused digital nudging in e-commerce.