There are also claims that council bosses are considering allowing picnics in a bid to attract younger people.
Shropshire Council library chief Gwilym Butler said the authority was "moving with the times" by relaxing the rules.
The council runs 22 libraries across the county, including in Shrewsbury, Oswestry, Market Drayton, Ludlow and Bridgnorth.
Councillor Butler, cabinet member for libraries on the authority, said: "Shropshire Council is intending to relax the rules on eating, drinking and mobile phone use in our libraries, to make sure that we move with the times and provide facilities that our customers want and need.
"There have been drinks machines in many libraries for a number of years so it makes sense to allow customers to bring their own drinks too.
"Snacks have also been allowed for a number of years at some libraries, and this is now being extended to the others – though we do put a limit on the consumption of hot food.
"The use of mobile phones is growing in libraries nationally and internationally.
"Customers use their devices to go online to gather information, apply for jobs and make appointments, as well as making calls to family and friends. They will now be able to do this in a safe and secure library wi-fi-enabled environment.
"It therefore makes sense that people are able to do all this in Shropshire's libraries."
Star comment: Libraries need to move on to survive
But regular library user Mike Brogden, from Shipton, near Much Wenlock, has criticised the move and said it would make libraries too noisy.
Mr Brogden said he also had been told by a senior librarian at the council that the authority was considering allowing picnics.
He added: "There have been no consultations with library users and the idea seems to stem from the Shirehall. I think that this would be a most unwelcome step."