It’s all happening online in grocery.

As The Co-operative Group and Morrisons prepare to make their long-awaited and much overdue debut online later this year, Sainsbury’s is ratcheting up the competition.

Just two weeks after the supermarket revealed its online grocery sales had hit £1bn a year for the first time, Sainsbury’s revealed today that it is building a ‘dark store’ in Bromley-By-Bow, East London, to boost its internet coverage in London and the South East.

The 185,000 sq ft online fulfilment centre is set to open in “the next few years” and will create 375 new jobs. Sainsbury’s Online, The Grocer’s reigning Online Retailer of the Year, already delivers to more than 190,000 customers a week, and says the centre will allow it serve 20,000 extra customers a week.

As The Grocer’s technology special issue this week shows, retailers large and small are embracing the e-pound. And all the big grocery retailers appeared in The Grocer’s list of the ‘Top 40 grocery apps’ – apps that we think are transforming shopper interaction between retailers, suppliers and shoppers.

But not everyone has mastered it… yet. The first-ever mobile Grocer 33 – tested on Asda, Sainsbury’s, Tesco, Waitrose and Ocado - revealed there was definite room for improvement, apart from Ocado which scored a perfect 25 out of 25 with our mystery shopper declaring they would “definitely use it again”.

Which just goes to show, get it right and you’re on to a winner. Getting it wrong just doesn’t bear thinking about.