As retailers gear up for a busy holiday shopping season, many are wondering how much e-commerce, and more specifically mobile commerce payments will contribute to overall sales this year. The quick answer is retailers need to embrace m-commerce.

Retail ecommerce is expected to be strong during this year’s holiday season: eMarketer estimates sales during the core holiday November–December period will reach $79.4 billion, an increase of 13.9% from the same time in 2014, continuing a multi-year trend of double-digit growth.  E-commerce’s share of overall retail sales will rise to 9% during the holiday shopping season, well above its predicted 7.1% share of total retail sales for the year.

Many shoppers use mobile devices to compare prices, research a local store or business, search for product information, and make purchases. M-commerce sales will grow 32% in 2015 according to eMarketer, far more quickly than ecommerce as a whole. This growth will be driven by increased use of smartphones for holiday purchases as larger screens, mobile-optimized webpages, newly-developed retail apps and easier mobile checkout processes are making buying on smartphones and tablets easier than ever.

So how does all of this information translate for retailers? There are a few trends that everyone interested in maximizing holiday sales should understand in order to take advantage of the growth in mobile commerce.

In a recent PayPal  global mobile survey of shopping trends, 47% of those who have shopped by mobile said that they prefer to use an app over a browser, for convenience and speed. So while many businesses have been focused on creating mobile-friendly sites, it is important to have an app strategy also. The same survey also found that a younger demographic, 18-34 year olds, accounts for 59% of mobile shoppers. For businesses whose demographic includes millennials, having a well-developed, easy to use app will be especially important.

The most successful retailers will give shoppers a seamless experience and be able to work with customers whether they walk into a store, order online, via mobile browser, via an app, or call on the phone. Being able to make a purchase on one channel and return to another is also important to consumers.

So that could mean ordering online and picking up or making a return in-store. The most successful retailers will unify their online and in-store merchandising, meeting and recognizing shoppers wherever they choose to engage with the brand.

If your business already has a mobile app, congratulations! You’re in a good position to benefit from the coming surge in m-commerce. If you still don’t have an app, don’t let another year go by before you solidify your app strategy and start building your presence in the mobile marketplace.

Anuj Nayar is senior director of global initiatives for PayPal.