Shoppers are flocking online for groceries. See who's winning over the most customers between Amazon, Walmart, Target, Costco, and more

• Amazon and Walmart are winning the war for online grocery spending, according to a new survey by Cowen & Co.
• The survey found that 53% of respondents shopped at Amazon for online groceries in the previous 30 days, compared to 44% at Walmart, 22% at Target, 15% at Instacart, 13% at Kroger, and 12% at Costco.

Americans are buying more groceries online than ever before, as they cook more meals at home and try to avoid virus exposure in stores.

The share of consumers who said they had purchased groceries online in the previous 30 days was roughly 33% in mid-August, compared to 18% one year ago, according to a Cowen & Co. survey.

As shoppers flock online for food, retailers are clamoring to win them over.

And so far, Amazon and Walmart are coming out far ahead of every other chain that sells groceries.

In the survey, which polled 2,500 people, Cowen asked shoppers which retailers they had purchased online groceries from within the last 30 days.

Amazon took the top spot with more than half of respondents — nearly 53% — saying they shopped there in the last month.

Walmart was closely behind with nearly 44% of respondents saying they shopped there recently, followed by Target (22%), Instacart (15%), Kroger (13%), and Costco (12%).

Overall, Cowen expects Walmart to keep winning market share over the long term due to its pickup services, express delivery, and vast store network, as Business Insider's Shoshy Ciment reports.