More and more, smartphones are becoming consumers’ go-to channel for online purchases. In 2015, eMarketer reports, retail mobile shopping, or retail “m-commerce,” almost doubled, and it expects the trend to continue through 2016.

The marketing researchers forecast 2016 retail m-commerce sales of $123.13 billion, up 39.1 percent over 2015, and more than double 2014’s $56.7 billion. This growth points to m-commerce accounting for almost one-third (32 percent) of retail e-commerce in 2016, and 2.6 percent of total retail spending.

Tablets account for most m-commerce and are expected to narrowly hold onto that majority in 2016, at 50.6 percent. However, the bulk of the segment’s growth is in smartphones. In 2015, smartphones alone accounted for $39.4 billion in retail m-commerce, up 95.8 percent from 2014. While eMarketer expects the segment to expand by a relatively subdued 49.9 percent in 2016, this growth still represents additional sales of nearly $20 billion. Smartphones will surpass tablets in 2017 and by 2020 are predicted to account for $129.4 billion in retail m-commerce in the U.S.