Marks & Spencer is expanding use of a "scan, pay and go" app-based service to all of its 573 UK grocery stores.
It first trialled the technology - which avoids the need to use a till - in London in March.
The retailer said it had "moved quickly" to make it standard as part of its response to the coronavirus pandemic.
Tesco, Sainsbury's and Co-op are among rivals that offer similar in-store shopping apps via more limited trials.
Others - including Waitrose and Asda - have apps that allow consumers to scan their purchases but still require payments to be made at checkout terminals.
The benefit of the M&S scheme is that it helps prevent consumers congregating in the same area at busy times.
"With the current restrictions in place, making shopping as easy and efficient as possible is really important to us and to our customers," said M&S's stores director Helen Milford.
"Mobile Pay Go helps do just that."
The service is accessed via the main M&S mobile app. However, it has a spending limit of £45.
The food-shopping industry had started investing in the use of such technology before Covid-19 struck.
Part of its reason for doing so was to head off a threat from Amazon.
The US firm plans to expand its Go stores to the UK, which use cameras and other sensors to track visitors after they enter and then automatically charge them when they leave.
"Amazon used to be the primary catalyst for change in the sector, forcing retailers to evolve and adapt for the digital era - and Covid will now finish what Amazon started," commented Natalie Berg, an analyst with NBK Retail.
"The pandemic is accelerating the adoption of in-store technology that, intentionally or not, facilitates a safe shopping experience."
The move also has the potential to save the business money if it reduces the need for as many staff and checkouts.
Earlier this month, M&S reported its first loss in 94 years, and in August said it was cutting 7,000 jobs.