The Challenge
As one of the world’s largest online resale platforms, ThredUp has a strong base of returning customers. But to stay ahead of competitors in a crowded fashion resale space, ThredUp wanted to attract more new customers. They knew they’d need to invest in marketing channels where fashion lovers were active and engaged if they hoped to accomplish this goal.
One place where fashion lovers certainly spend their time? Pinterest, where enthusiasts fill their boards with pieces they’d love to add to their wardrobe. “People come to Pinterest to find ideas and inspiration,” says Haus Measurement Strategist Noah Gramitt (ex-Pinterest). “It’s visual first, making it uniquely effective for showcasing products for discovery. For a business like Thredup, it’s one of the best places to test into reaching an incremental audience.”
The team at ThredUp was already spending a bit on Pinterest without much signal on performance, but they believed they could dig in even more and scale their presence on the platform. To test this hypothesis, they turned to Haus.
The Solution
The ThredUp team designed a 2-cell holdout test in the Haus app to establish a baseline for Pinterest’s incremental impact, using New Purchasers as the primary KPI. For five weeks, half of their audience wouldn’t see ads, while the other half would. Since purchasers might take a while to consider an item, they set up the test for a longer duration and included a two-week post-treatment window to measure lagged effects.

The Result
The results of ThredUp’s holdout test blew away expectations, driving a 1.53% lift in New Purchasers. Plus, the platform drove New Purchasers efficiently, with a CPIA that was 40% lower than their goal.
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The ThredUp team is thrilled with the results and plans to scale up Pinterest over the coming weeks before testing again at a higher spend level to validate how far they can scale spend on the platform. The team is bullish on scaling Pinterest and sees the channel as a major opportunity to reach new audiences going forward.