More than two million Muslims will descend upon Mecca this weekend.
The Hajj is an annual journey to Mecca, a desert valley in Saudi Arabia, that all able-bodied and financially capable Muslim adults are expected to make at least once in their lifetime.
It is the world's largest annual pilgrimage, and this year there is an effort to use technology like never before, to make it as safe as possible.
The Ministry of Hajj and Umrah has worked with the Saudi Communications and Information Technology Commission to set up extra cell towers and Wi-Fi spots to connect loved ones unable to perform the Hajj to those on the journey.
An app for 2018 is also the first in a series of plans to use technology to re-design the event by 2030 (see below).
What is the Hajj?
The Hajj takes place on the eighth and twelfth days of the final month of the Muslim calendar: between Sunday 19 August and Friday 24 August in 2018.
The five-day pilgrimage is the fifth and final pillar of Islam, and concludes when up to two million Muslims circle the sacred cube-shaped Kaaba, a building at the centre of the religion's most important mosque.
In 2016, up to 1.8 million Muslims took part. An estimated 221,000 came from Indonesia, 179,210 from Pakistan, and 170,000 from India and Bangladesh and Egypt. The majority, 1,082,228, were male and 780,681 were female.
More than 51,000 government staff work around the clock during the Hajj.
Why is the ritual so important?
Mecca is considered the most holy city for Muslims and the journey resembles a tradition performed by the Prophet Muhammad with millions of Muslims undertaking a route around a rocky mountain of the ancient city, where the Prophet Muhammad once traced the movements of the Prophet Abraham and Ishmael.
In Islam, the Hajj represents the actions of the Prophet Muhammad in a pilgrimage dating back to 632 AD. The ritual cleanses faithful Mulsims of sin and brings them closer to God.
A total of 1.8 million Muslims took part in the Hajj in 2016. That number jumped to more than 2.3 million pilgrims in 2017.
What happens on each day?
Pilgrims enter the sacred city of Ihram in plain white clothing. They then travel to the small town of Mina. Here Muslims will spend a day and night in the sprawling tent village.
Known as the 'Day of Arafat' all pilgrims converge near Mount of Mercy after a 14.4km journey. Muslims stand or sit to pray. Following prayer, Muslims travel 9km to Muzdalifah and collect pebbles for the next day.
Pilgrims travel back to Mina and throw the stone pebbles at pillars. The act resembes casting away the temptations of the devil.
Next Muslims must slaughter a sheep, goat, cow or camel - to complete the re-enactment of when Abraham went to sacrifice his son, only to find God had placed a ram there to be slaughtered instead.
Muslims give away the meat to the poor as a gesture of parting with something precious.
Finally, the last couple of days are dedicated to travelling to the Grand Mosque in Mecca and circling the Kaaba seven times.
Stampedes and political issues
The Hajj has been marred with deaths in recent years. In 2015, Saudi Arabia officials claimed more than 717 people were killed due to a stampede in Mina. More than 360 pilgrims died in a stampede the following year.
Tensions in the Gulf region also reached a critical point in 2017 after Saudi Arabia, the United Arab Emirates, Bahrain and Egypt severed diplomatic ties with Qatar after they alleged the nation was supporting terrorism.
In June 2017 the crossing between Saudi Arabia and Qatar, the Salwa border, was blocked. All Qatar Airways flights were also banned during the Hajj.
Since the dispute, Saudi Arabia's King Salman ordered the reopening of the border and relaxed its restrictions on flights. This year he is reported to be paying for hundreds of Yemeni and Sudanese families to attend the Hajj. The families will be relatives of soldiers killed in Yemen's war.
For years, Yemen has been involved in a war between Houthi rebels and supporters of Yemen's internationally recognised government. Since 2015, Saudi Arabia formed a coalition of Arab states to defeat the Houthis.
Can an app improve safety in 2018?
Government officials are making a big effort to make sure the Hajj is as safe as possible. As part of the initiative more than 16,000 communication towers and more than 3,000 Wi-Fi hotspots will be set-up.
This will allow pilgrims to use the 4G mobile network at all times in order to maintain contact with families and to use the ministry's online services.
The ministry's Smart Hajj app can be downloaded to help pilgrims perform the Hajj with a step-by-step guide, satellite map and information in seven different languages.
The app also has GPS technology so pilgrims can locate their companions during the Hajj and find the shortest route to reach them. With just one-click emergency services can also be called.
The Ministry of Hajj and Umrah also released a video showing how technology could further improve the event by 2030. It suggests one day all attendees will get a digital ID card, electronic bracelet and earpiece.
Watch the video below:
Advice for Australians planning to attend the Hajj can be found at smartraveller.gov.au