Last Black Friday, 4 out of 10 online shoppers were on mobile devices.  This year it was expected that for the first Thanksgiving weekend ever, retailers would see more traffic from customers on mobile devices than from laptops or desktop computers.

But would this be the year that mobile surpassed desktop? And would we see a spike not only in mobile sessions but also in other metrics like average order value and conversion rates?

We selected a sample of twelve leading retailers from across a spectrum of the retail industry - including health, gifting, home and garden and apparel - to track the year-over-year growth in mobile in our 2014 Mobile Holiday Shopping Report.

What we found is this holiday weekend did in fact mark a tipping point for mobile - and retailers on our platform saw dramatic year-over-year mobile growth.

On Thanksgiving Day, retailers in our sample saw 38.1% more sessions from mobile devices than they did last year. Black Friday's year-over-year mobile** session** increase of** 45.6% **was even more significant.

Not only did the retail sites in our sample see more mobile sessions on both Thursday and Friday, the mobile experiences the retailers provided were also better at converting mobile customers.

Mobile conversion rates on Thanksgiving increased by** 9.9%** year-over-year. And on Black Friday mobile conversion rates increased by more than twice that, 21.7%.

Although the year-over-year growth rate of mobile sessions was 1.2 times for Black Friday what it was for Thanksgiving and the mobile conversion rate growth was 2.2 times the size, Black Friday had a lower spike in mobile revenue from last year than did Thanksgiving.

The lower, though still very significant, year-over-year mobile revenue increase for Black Friday versus Thanksgiving is related to the lower increase in Average Order Value (AOV).

AOV increased by 4% year-over-year, versus a 25.2% increase for Thanksgiving, likely because of steeper discounts offered by retailers on Black Friday.

Overall, the trends we saw on Thanksgiving and Black Friday show that there has been a definite shift in online shopper behavior, with significant year-over-year growth for mobile.

Last Cyber Monday, we saw a spike in some metrics from Black Friday to Cyber Monday. Will this year be similar?

Stay tuned for more updates here on our blog and in our report, as we dig deeper into the numbers.

by Anis Salvesen