“I fell in love with consignment because it’s a way to have beautiful things on a budget,’’ says Revolve consignment boutique owner Lisa Castagno.

Shoppers have fallen in love, too. Trendy secondhand boutiques have cropped up as brick and mortars like Revolve and online shops like thredUP and Tradesy are drawing increasing numbers of younger customers, who like frequent fashion updates and the thrift of the sharing economy.

Boutique consignment has grown more popular for three reasons, Castagno speculates. First, in this era of Instagram and Facebook, it’s possible to track rising trends in real time. There’s also the potential horror of being snapped in the same outfit twice, and people are motivated to rotate their wardrobes regularly.

Secondly, “Shoppers are value-conscious now,’’ says Castagno, whose first Revolve, in Belmont, opened in November 2009 at the recession’s height (she recently opened a sixth on Newbury Street). Her customers check consignment prices, which tend to be at a significant discount from retail ones, with their phones while browsing to ensure that hers are competitive.

Then there’s the de-cluttering craze, probably fueled by minimalist organizer Marie Kondo and reflected by interest in the tiny-house ethos. Many consignors long to purge but feel guilty tossing out luxury items or ones that have sentimental value. Perhaps they traveled to Italy with one piece or got engaged in another. “People have full closets of things they don’t use and a close connection to their own things,’’ says Castagno. Consignment boutiques ensure that these divested duds find good homes.

“Once, people felt uncomfortable about consigning. They were nervous about buying something secondhand. That has really disappeared: Consignment stores are becoming more like real boutiques. It’s not your grandmother’s thrift store,’’ Castagno says.

Kara Baskin can be reached at kcbaskin@gmail.com.