(CNN) — The UK travel rules have gone through many changes over the past few weeks.
Just days after new destinations were added to the nation's "green list," a number of countries, including Majorca, are already being dropped back to "amber" status.
The latest amendment comes as travel regulations, along with the risk-based "traffic light" system, continue to cause widespread confusion among those eager to take a vacation since the ban on foreign holidays was lifted in May.
Here's everything you need to know about the UK travel rules, including the latest additions to the green list and the green watch list, as well as upcoming changes regarding amber-designated places.
Can UK residents now travel abroad for a holiday?
Residents of England, Scotland and Wales have been allowed to go on vacation since May 17, when the restrictions that made it illegal to travel abroad for nonessential reasons ended.
The rules were relaxed for residents of Northern Ireland on May 24.
However, the UK government officials has continually warned travelers that the experience will be very different because of ongoing concerns around Covid-19.
"I want to stress that this is going to be, whatever happens, a difficult year for travel," UK Prime Minister Boris Johnson told reporters on June 21.
"There will be hassle, there will be delays, because the priority has got to be to keep the country safe and stop the virus coming back in."
Previous rules around social distancing in England were lifted on July 19, while wearing face masks is now voluntary in all settings.
What are the green list countries?
Seven Mile Beach on Grand Cayman island. The Cayman Islands are currently on the "green list."
The UK's traffic light system for designating safe travel destinations lists countries or territories it classifies as safest as "green" -- meaning anyone traveling there will not have to quarantine on return.
What follows is the full green list, as of Monday, July 19. The destinations in bold are currently on the "green watchlist," which means they're in danger of moving to amber:
Antarctica/British Antarctic Territory
Antigua and Barbuda
British Indian Ocean Territory
Madeira (autonomous Atlantic island group belonging to Portugal)
South Georgia and South Sandwich Islands
St Helena, Ascension and Tristan da Cunha
Turks and Caicos Islands
Portugal was originally on the green list, but it moved to amber on June 8.
It's worth noting that entry to Australia, Brunei, the Faroe Islands, New Zealand and Singapore is heavily restricted, so a destination's appearance on the list doesn't automatically mean that UK travelers can go there.
Which countries can I visit if I live in England?
English travelers are permitted to the "green" destinations without having to quarantine on their return, provided they take a predeparture test, as well as a PCR test on or before day two of their arrival back in the UK.
That said, some countries currently listed as green, such as New Zealand and Australia, remain closed to international travelers.
While travelers are also allowed to visit countries designated "amber" or "red," the restrictions are much stricter, making them far less attractive options.
Those who choose to visit places on the "amber" list, which include Portugal, Greece, Spain and Italy, and are not fully vaccinated will have to quarantine for 10 days when they return, take a predeparture test and also get a PCR test on day two and eight of their isolation.
However, "amber" destinations -- with the exception of France -- qualify for a test-to-release scheme, which means holidaymakers can take a PCR test after five days' quarantine. If they receive a negative result, they will be permitted to go out into the community.
UK Transport Secretary Grant Shapps has confirmed that, from July 19, UK residents arriving from amber list countries "who are fully vaccinated through the UK vaccine rollout" won't have to quarantine. Again
But residents will still be required to take a Covid-19 test before they return home and a second test on day two.
While children under the age of 18 will no longer have to self-isolate, they'll also be required to take tests, according to Shapps.
The move came as British Airways and Virgin Atlantic revealed plans to trial fast track lanes for fully vaccinated travelers arriving at Heathrow Airport on selected flights.
Four routes will be covered in the scheme, which will allow passengers on flights from Athens, Los Angeles, Montego Bay and New York to Heathrow upload their vaccination status before boarding the aircraft.
Travelers from England who choose to visit "red" list destinations are required to check in to one of the UK's quarantine hotels, at a cost of £1,750 (around $2,445) per adult when they return. They must also follow the same testing regulations as those arriving from "amber" destinations.
Which countries can I visit if I live in Scotland, Wales and Northern Ireland?
The separate "green lists" released by Scotland, Wales and Northern Ireland have been identical to England's so far.
However, the destinations included may change according to each countries' needs.
How is the UK deciding which countries go on its lists?
The UK government has said the decision-making is based on factors including a country's Covid-19 transmission risk, its variant of concern transmission risk and its genomic surveillance capability.
The UK's Joint Biosecurity Centre has undertaken risk assessments for each destination, using data including total number of vaccination doses administered per 100 people. You can read more about the data used here, and about the methodology here.
Should I book a summer holiday in a country on the amber list?
The amber list contains some of the UK's most-loved tourist destinations, such as Portugal, Italy, Greece, Spain and France.
The government guidance is that UK residents should not be booking holidays to "amber list" countries, or planning any nonessential travel, but it is no longer illegal to do so. The amber list is subject to change, which means countries may move to green or red at any time.
Can I go on holiday in the UK?
Travelers from England, Scotland, Wales and Northern Ireland are allowed to go anywhere within those countries and overnight stays are permitted at hotels, B&Bs and hostels, though rules around group numbers vary in each destination.
Those who plan to visit any of the Scottish islands are advised to take two lateral flow tests before their trip.
Will I have to quarantine when I come home?
Quarantine rules depend on whether the country you're traveling to/from is on the "green," "red" or "amber list."
If you are arriving into the country from a "red" list country, you will have to quarantine in a designated hotel upon arrival for 10 days at your own expense. Bookings must be made through this online portal. The charge for a single adult is £1,750.
There are designated quarantine hotels in England and Scotland. If your final destination is in Wales or Northern Ireland, you will need to book a hotel in England or Scotland.
If you are arriving from an "amber" list country, you will have to quarantine at home for 10 days. The other people in your household do not need to quarantine with you, unless they were also on your trip, or they have Covid symptoms, or they test positive.
If you are arriving from a "green list" destination, quarantine is not a requirement. The quarantine requirements work in tandem with testing. It's compulsory to take a Covid test on or before day two of your quarantine, and on or after day eight.
If you are arriving in England from an "amber" country, it's possible to end your quarantine early via the Test to Release system. This involves paying for a private test, if it's negative, you can end your quarantine period. It's not possible to do this until you've been in England for at least five days.
If you're arriving from a "red" or "amber" destination, your passenger locator form must contain details of your quarantine destination.
You can get public transport to your place where you intend to quarantine, but the official guidance is to only do so "if you have no other option." For the full rules, see here.
During your quarantine, you will be contacted by NHS Test and Trace.
When will the rules change?
The UK government has said the "red", "amber" and "green" list will be "continuously monitored" and updated every three weeks, so it's worth keeping tabs on a destination before you depart. There's no guarantee that a "green" country will stay that way.
As for the system more generally -- the guidance says travel restrictions will be formally reviewed on June 28, no later than July 31 and October 1, 2021.
Will I need to be vaccinated to travel?
Some countries, such as Iceland, are now open to international travelers who can present proof of vaccination. In the absence of this, sometimes a recent negative Covid-19 test, or proof of recovery from Covid-19 will also suffice.
The rules frequently change from country to country, and it is advisable to check destination-specific requirements before booking travel and closer to departure.
Will I need a Covid test to travel?
Yes. Travelers heading to approved destinations will need to take a predeparture test, as well as a PCR test on or before day two of their arrival back in the UK.
A test may be needed by the country you're traveling to. Most destinations that are open to arrivals now require a recent negative PCR test before visitors can enter.
Portugal, currently on the "amber" list, will now accept lateral flow tests for those arriving from the UK, along with EU and Schengen countries.
When can UK citizens fly to the United States?
The US is currently on the UK's "amber" list. As explained above, the UK does not advise nonessential travel to "amber" countries. Plus, UK residents have been banned from entering the United States since March 2020 and this ban is still in place.
When the initial "green list" destinations were announced, the World Travel & Tourism Council expressed disappointment that the US was not included and accused the UK government of being "too cautious."
Airlines have also been clamoring for the reintroduction of the transatlantic travel corridor, one of the world's busiest air routes during pre-pandemic times.
It's unknown when the United States might make it onto the "green list," but it'll likely coincide with a lifting of US restrictions on UK travelers.