But by 9am the website had closed again, saying it had already received all the orders it could process for the day, but it would return on Wednesday.
The retail giant closed its online operations in late March amid the coronavirus crisis, following criticism from staff who felt unsafe at work.
Behind the scenes, bosses have been upgrading warehouse space and limiting workers to accommodate the Government's distancing measures.
A statement posted on the Next website said warehouse managers had "successfully tested opening and taking a limited number of orders today".
But by 9am the website had stopped taking orders, with a message reading: "No more orders today, we're open again tomorrow.
"We have successfully tested opening and taking a limited number of orders today. Please come back again tomorrow morning."
The group has started selling childrenswear and some small home items, with more ranges planned at a later date, prompting shares to rise 2% on the FTSE 100 index.
Next said the online service will operate with staff who are "willing and able to safely return to work", with a small number in each warehouse at any one time.
Only a limited number of orders will be allowed, with the group pausing orders if it needs to and converting the website to "browse only" until the following morning to keep staff and item pickers safe.
It comes after Next was forced into a U-turn over its initial decision to keep warehouses open for online orders after sustained pressure from politicians and staff.
Last month it was revealed that the company had offered a 20% pay rise to any worker willing to continue picking clothing for customers.
Bosses at the chain say they have spent two weeks "reworking" warehouse operations and have taken "lots of practical measures" to ensure that staff who want to work "feel safe, work safe and are safe".
"In order to operate our warehouse safely, we are limiting the number of warehouse colleagues working at any time, and so we will limit the number of customer orders we can take each day," said the statement.
"We have put extra safety measures in our warehouse to ensure our colleagues can work safely for you."
A video on the website explains safety measures for warehouse staff. They include two-metre floor markings to help maintain social distancing, a one-way movement system, and sanitising stations.
Staff will also wear tabards marked on the back with the message "Stay 2 metres apart" and will be given "keep clean kits".