Thousands of people have turned to online supermarket shopping for the first time this year - but how much do you know about how it works?
The pandemic has massively increased the number of people ordering their groceries online. For months, shielding people were instructed not to go to the shops at all, and millions of Brits continue to avoid visiting stores where possible.
In fact online grocery sales in September were up 76% compared with the same month last year, according to market analyst Kantar Worldpanel, with one in five households ordering groceries on the internet. The proportion of grocery purchases made digitally was about 12.5%.
But even if you've used online supermarkets for years, you may be surprised by how it all works. Here, we reveal our favourite supermarket secrets and explain how to have the best experience when shopping online.
Have you ever thought about who picks your online grocery shopping?It all depends on which supermarket you shop with and where you live.
Often, it's picked by a member of supermarket staff in a normal store while members of the public do their own shopping - you might have seen them wheeling crates around the aisles.
Other times it's picked by staff in a so-called 'dark store' - an area attached to the supermarket that isn't accessible to the public - or a more conventional warehouse.
And finally, if you shop with Ocado, your groceries could be picked by robots kitted out with grippers that mimic a human hand and advanced vision systems which allow them to recognise different sized and shaped packages.
Shopping online gives you easy access to a range of great discounts - in fact, you can usually browse them in their own dedicated section.
But watch out for the small print: sometimes the discounts will expire before your delivery date, meaning you end up paying full price.
Among the most entertaining we've heard of are Kettle Chips instead of an electric kettle, Kiwi shoe polish instead of
kiwi fruits, an Asda shopper ordering candles and receiving electric candle bulbs instead, and - possibly strangest of
all - a Sainsbury's customer who wanted fabric conditioner and was instead presented with a lemon.
But substitutions aren't always a laughing matter. Spare a thought for the vegetarian Tesco shopper who ended up with pork sausages instead of Quorn ones, and the diabetic Asda customer who was sent a sugary bottle of pop instead of the diet version.
On the flipside, substitutions can sometimes work in your favour if the supermarket has a price promise meaning you only pay for what you ordered, even when a pricier item is swapped in.
If you don't like the replacement you're given, you can return it, but if you'd rather avoid the faff altogether you can ban substitutions entirely or - depending on the supermarket - on an item-by-item basis.
You might assume that product reviews on supermarket websites build up naturally. Well, think again.
Some products have hundreds - or even thousands - of reviews, while other similar products have barely any. When we looked at fabric freshener spray on the Tesco website in March, it had just two reviews, while the branded Febreze equivalent had 1,413 - all submitted through a reviews site run by manufacturer Proctor & Gamble.
Industry experts claim that just a few product reviews can significantly boost sales and there is a whole sub-industry of marketing experts working to increase grocery reviews. So how does it work?
Firstly, marketing agencies and manufacturers identify products they want to increase reviews on. These might be ones that have low numbers of reviews, products they want to feature higher in search results or new launches. These agencies then send free samples or money-off coupons for the product to targeted groups of consumers, asking them to write a review.
While none of this is against any laws, it's worth being aware of what happens behind the scenes before buying groceries based on their online reviews.
Product placement is arguably even more important on supermarket websites than it is on shelves because it's harder to browse for inspiration when you're online.
We checked search results for five of the most popular branded and own-brand groceries on all the major supermarkets' websites in March, and asked experts Dr Jeff Bray and Dr Julia Hibbert from Bournemouth University to help us analyse the results.
Some supermarkets, including Asda, Tesco and Waitrose, ordered results by 'relevance' as the default. Others, such as Morrisons, Ocado and Sainsbury's, sorted them by 'favourites', which our experts concluded must be the supermarkets' choice of products given that we hadn't selected any favourites and had turned off browsing history and cookies. Meanwhile Iceland listed search results by 'bestsellers'.
We also found examples of supermarkets offering up brands and products we hadn't searched for- for example, Sainsbury's cheekily suggested gin to go with our Cadbury Milk Tray. Dr Bray said: 'Just as with shelving placement, the order items are presented in and how they are juxtaposed can have a big impact in guiding us toward particular choices.'
If you're after inspiration then this is great - but don't get persuaded into buying things you don't really need.
If you want to book a slot but don't yet know exactly what you'll want to eat that week, just order with placeholder items in your basket (our researchers tend to add a bottle or two of pricey Champagne), and then amend your order closer to the time.
Just make sure you check how close to the delivery date you can do this, as it varies by supermarket, and - unless you actually want it - remember to remove the fizz before your final checkout.
Delivery pass schemes where you pay a set amount for 'free' delivery each month or year are another good way of securing slots in advance. Many supermarkets allow their most loyal customers priority access to slots, including those in the run-up to Christmas.
Our experts crunch thousands of grocery prices to reveal the cheapest (and most expensive) supermarket each month.
Our latest supermarket price comparison compared the price of a trolley packed with 103 items, including Branston baked beans and Flash cleaning spray, at the six biggest online supermarkets.
Asda, at £181.69, was the cheapest supermarket in October and pipped its next-closest rival (Sainsbury's) by £7.50. Ocado was the priciest online supermarket, with our trolley of groceries costing £211.49.
When you think about it, £1 - or even £7, if you're shopping with a pricier supermarket - for the convenience of having someone else do all your grocery shopping and bring it to your door is a bit of a bargain.
While online grocery shopping is a big time-saver for customers, it doesn't make much - if any - profit for supermarkets. That's because of the overheads: the money needed for drivers, refrigerated delivery vans, storage areas, pickers and packers is huge.
Indeed, the UK's two largest supermarkets - Tesco and Sainsbury's - have both said they don't expect increased profits this year despite selling vastly more food due to people being stuck at home.
It's no coincidence that discounters Aldi and Lidl haven't yet taken the plunge into full-scale online deliveries. And how to make a decent profit from online shopping is one of the biggest issues facing the supermarket industry right now.
Some supermarkets even charge different prices for the same products in store and online.
M&S, which teamed up with Ocado earlier this year, hit the headlines recently after it emerged some products were priced differently in store from online with Ocado.
A spokesperson for Marks & Spencer said that M&S and Ocado are two separate businesses, which means Ocado sets its prices independently. Ocado said most M&S products were similarly priced on its website and in stores.
Ordering groceries via delivery app Deliveroo is also becoming increasingly popular. Sometimes groceries ordered this way can cost more than in stores - although not always. There's also delivery fees and other charges to take into account.