The lovebirds are tying the knot at St. George's Chapel in Windsor, England, on Saturday, and have invited 600 guests to watch them say "I do." Now, a source tells ET that those lucky guests will have their cell phones seized upon arrival.
According to our source, the same protocol was in place when Prince William married Kate Middleton at Westminster Abbey in London in 2011.
The night before the wedding, Meghan and her mother, Doria Ragland, will stay at the Clivden House Hotel, while Prince Harry will spend the night at Dorchester Collection's Coworth Park. ET has learned that both of the hotels will have heavy security, but will not be on lockdown.
"There will, of course, be an extreme amount of royal guards on both properties," the source says. "Meghan and Harry will each have their own wing in their perspective hotels. Both hotels will remain open to the public, but guests will have zero chance of getting anywhere near the royals' private wings."
ET also spoke with security expert Alex Bomberg, CEO of International Protection International Limited, on Wednesday, who explained the similarities and differences between Meghan and Harry's nuptials with Kate and William's wedding.
"This is a medieval town," he says of Windsor. "It's not used to events of this size. While it's used [for] a lot of royal events, it's not used to hue weddings of this size. So, this is certainly a challenge, logistically, and police-wise. Crowd management here is going to be the real problem. That's going to be the major issue here."
"The situation you've got here is you don't have the facilities in place for the security to really take place. They're starting from scratch here -- really difficult situation," he continues. "London, Buckingham Palace, they're used to major events there all the time. This is something very, very spectacular here in Windsor."
Details about Meghan and Harry's extensive wedding day security measures were first revealed in March by the Thames Valley Police. At the time, they anticipated that the massive security operation will be among the largest in Thames Valley Police’s history, attracting over 100,000 people from around the world to Windsor.
"We are proud to police the Royal Borough of Windsor and Maidenhead," Thames Valley Police Assistant Chief Constable David Hardcastle, strategic commander for the wedding, said. "The Force has a long history of policing Royal events from the annual Windsor Garter Ceremony to state visits and more recently Her Majesty the Queen’s 90th birthday."
"The wedding of Prince Harry and Ms. Markle is no exception," he added. "We are working with our partners, local businesses and the community to deliver a safe, secure and happy event for everyone."
When it comes to security, it seems Meghan and Harry will have nothing to worry about. But one thing they are concerned about in the days leading up to their big day is the former Suits star's father, Thomas Markle, who is reportedly having some health issues.
Thomas told TMZ on Tuesday that he would not be attending his daughter's nuptials because he has to have surgery on Wednesday after suffering a heart attack a week ago, though he told the outlet earlier in the day he was looking forward to walking his daughter down the aisle. This update comes just a few days after Thomas originally backed out of the wedding after he was accused of staging photos for the paparazzi.
"This is a serious situation. Meghan and Harry are very concerned," a source told ET. "Thomas' health is a private matter and therefore no comments or statements will be made [by the Palace]."
"Meghan and Harry have mixed emotions right now, between their concern for Meghan's dad and the exciting start of their life together," the source added.
Hear more in the video below, and keep up with all of ET's coverage of the royal wedding as we count down to May 19.