NEW YORK — Cyber Monday remains the busiest e-commerce shopping day of the year, according to an analysis by Chase.

Cyber Monday remains the busiest e-commerce shopping day of the year, according to an analysis by Chase.

Online sales on the first Monday after Thanksgiving were up 21.8% over last year. Monday sales topped the Sunday after Thanksgiving, the next highest day for online sales, by a margin of 26.7%.

Online retailers have also made inroads on shopping days more traditionally associated with in-store shopping. Online sales on Black Friday topped $1 billion for the first time this year, according to comScore Inc. That is an increase of 26% over last year, comScore said, adding that Amazon.com was the most visited retail website on Black Friday, followed by Walmart.com, BestBuy.com, Target.com and Apple.com.

ShopperTrack estimated that Black Friday sales in stores this year totaled $11.2 billion, down 1.8% from last year.