Better Seller Experience on C2C e-Commerce App

Carousell Design Challenge

A new design for better selling experience –

Easy interaction to manage multiple offers and negotiate to get the BEST offer

Duration - 1 week        Team of 1        Role - Designer  

Carousell as one of the main c2c marketplace for selling and buying new and second-hand goods online in Asian countries has its niche in providing easy interaction and smooth trading experience for both sellers and buyers. To keep the marketplace growing, Carousell has great community support for each sub-market, providing instant help and maintain order, and thus attract sellers and buyers to continue trading on Carousell. 


The process of posting an item for sale can be as quick as 30 seconds – take a picture, input the product name and category, post it, and the rest is just getting offers from buyers, and chatting in the in-app mailbox with the buyers to accept the offer. 

However, as some goods are more popular than the others, such as highly valued items like iPhone, watch or accessory, sometimes a seller might get a overwhelming number of offers and can’t manage to sift through multiple chats and offers. It is hard for the seller to consider price, timing and location all at once while negotiating with potential buyers. Thus, in this design challenge, I was asked to design on top of the existing app to solve this challenge –

        How to make it easier for the seller to accept the best offer?

So, in order to tackle this problem, I started from researching related products and user behaviors to come up with and answer the following questions – How did other products work to serve similar function? What are users’ mental model when they are facing multiple offers to negotiate with? What factors are most important in the decision making process? And from the product design point of view, what features can I design on Carousell to best address this challenge and optimize user experience?


Before I jumped into the research and design process, I first quickly fetched some related information in my head and outlined a few directions for research. To compare a list of offers, ranking, parallel listing and comparing, and filtering results are common methods. Alternatively, auction/public bidding is also an attractive way for buying and selling, as some of the shopping apps competitors have applied. 

With that in mind, I defined 3 critical categories to conduct my research on- 

  1. User experience, app interface and features on existing services
    - Carousell, Facebook, Yahoo Bid, Shopee, Craigslist, etc.
  2. Comparing and purchasing process for highly valued items
    - Car, Antique, Housing, Electronic Devices, etc.
  3. User need, priority and behavior under this condition
    - What do they value the most? Sell it ASAP (timing), higher price (price), easier communication & delivery (location)…
    - What features can help them better sort / compare the results?

C2C Online Trading Service

Since Carousell is my target design product, I spent quite a while researching its design and trading process. Besides, as Facebook group serves as the main used-goods trading platform for students in the US, Yahoo Bid as a main player in c2c e-commerce market in Taiwan, I researched their features and analyzed the logic behind the design. 

A critical difference behind the product design for selling items is whether they allow buyers to know about other buyers’ offers. 

YES- Facebook group, Yahoo Bid

- More transparent
- A explicit rule for buyers to follow
- Require less communication 
- More efforts needed for the buyers
- Sellers can’t fully control the result
- The price may be cut down on purpose 

NO- Carousell, Shopee

- Simpler process for buyers
- Sellers have full control over the decision
- Sellers can get the offer closer to expectation
- Require more communication
- Buyers know few about the deciding process
- The decision may be unfair to the market due to seller’s own preference

As Carousell serves more as a c2c trading app than an e-commerce marketplace for bigger sellers, it makes sense to keep the scale smaller and more private to allow full decision in sellers' hand, which thus encourage sellers to keep selling items on the platform.

As a result, when I brainstormed possible solutions for the seller to deal with multiple buyers, making the process to go public and include bidding was not chosen because of Carousell’s present market positioning and users niche.

Purchase of highly valued merchandizes

As buyers are willing to spend more time on highly valued merchandizes, like cars, antiques and house, the process of offering, comparing, negotiating and deciding takes more efforts but also involves more logical thinking. Sellers and buyers would compare available offers carefully and make the best out of it. This process is similar across all expensive products and thus very relatable to the challenge here for Carousell — make it easier for the seller to accept the best offer. 

I looked into several examples such as Proxibid, Google Mortgage, for buying or selling car and mortgage. Live auction and timed auction are common for antiques that are rare, while for practical products like house or a used car, detailed comparing sheets or standardized form are provided to make sure customers can get the best offer. No matter it’s an interactive visual design, organized excel sheet, or a high-to-low price list…they are all meant to provide comparison for customers and help them make decision. 

User Behavioral Insights

As the result of my research on related products and analysis of users behaviors and mental status, I obtained some valuable insights for the online purchase where comparison and decision of multiple offers are happening-

  1. For highly valued items, users valued “Price” the most. For things like cars, antique, or house, a seller wouldn’t bother to compare more offers and make negotiation.
  2. If the seller and buyer are going to “Meet-up” for trading goods, location and timing would become a concern, while these two factors make no difference if go by “Mailing or Delivery”.
  3.  “Payment” method and security becomes a concern for expensive goods. Buyers might want to check the product’s quality before paying while sellers want a deposit and make sure to get payment safely. 
    -> That’s why third-party payment such as paypal and Alipay becomes indispensable for e-commerce market. 

Research Insights

          Carousell keeps the negotiation process simple and private to encourage
          more non-business sellers to engage.

So right here after quite a few research, I know more about what’s out there for mobile/online shopping market, what different design logic behind the services they provide, and what differentiates Carousell with its competitors – that is, instead of providing a public bargain market and end-to-end full service including payment solution and logistics, Carousell keeps the negotiation process simple and private to encourage more non-business sellers to engage.

Also, although the implementation differs, the way to solve complex decision making process among multiple offers for higher valued products is through comparison and negotiation. 

          How to highlight the most critical component, “Price”, and make the
         negotiation among multiple offers easier is the core of the design.


Moodboard & Brainstorming 

During the brainstorming, I first came up with features to visualize main factors like price, location, and timing, including bar chart, calendar and filter. Then I thought about the negotiation process, where sellers can either contact a few top buyers after comparing offers or choose to “go public” to enter a bidding system to let buyers compete for the product. 

However, considering the existing product features, bidding is not suitable for Carousell’s presence in the market. Thus, another feature “Broadcasting message”, which helps to make easy negotiation by messaging multiple buyers after comparing offers, is chosen to develop for next step.

User Flow

As I decided on the ideas of filtering and broadcasting message, I depicted a user flow that cover the complete comparing, negotiating and accepting selling experience.

A seller posts a product to sell
→ get messages and offers from multiple buyers
→ filters offers based on price, location, delivery choices and reviews
→ negotiate with potential buyers
→ accept offer and deliver the product

The most chaos happens in the middle of the user journey– filtering offers, deciding which offers to chat to, and negotiating among multiple potential buyers. And this is what my following design tries to solve.

Initial Sketches

I fleshed out the functions I designed, filter and broadcast, and made improvement on the metadata of each message to provide marking feature and highlight important components a seller cares the most, including price, review, and deliver choice. 


After a few iteration and modification of interfaces design in Sketch, I brought the high-fidelity mockup into Principle and made it interactive.

Final Design


The final design includes a high fidelity implementation of key screens and an interactive prototype to visualize the user interaction. 

Apply Filters

The seller in this use case, let’s say Tom, is selling an Apple Watch at $150 and got multiple offers. He applied the filer to filter offers with price range in $100-$150, getting the product by meet-up in Taipei city, and buyers with no bad reviews. 

It helps him to cut down a great number of offers, and also allows him to view the results in both list and grid view, mark the preferred chats and sort them based on price, timing or other conditions. The color bar on each offer, from red to grey, indicates how close the offer aligns with his expectation, a.k.a. a better offer.

Broadcast messages to filtered offers

After filtering offers based on requirements, Tom wants to negotiate with them all at once. By clicking “Broadcast”, he is able to send a message to all filtered offers, marked or selected buyers, to confirm meetup timing and location, with some default sentences to choose from. By this broadcasting system, he will be able to accept whichever confirms the first!

While I designed mainly on top of the existing Carousell features and visual language, I also made some improvement on the metatdata and visual layout to highlight important components like price or review counts, and add filtering and sorting features to improve interaction for sellers. 


Finally, here is a design patch of the visual design and icons I made for the prototype!