How do Orthodox Christians celebrate Christ's resurrection on Easter Sunday? After checking the Orthodox Christianity and Easter tags (over 400 of them), I could find nothing specific on how Orthodox Christianity celebrates Easter Sunday, apart from the Paschal greeting What is the earliest surviving reference to the Paschal Greeting? , and one custom of the breaking of pottery on a few of the Greek Ionian islands. In Corfu it happens on Holy Saturday where ceramic pots are thrown off balconies into the streets.  In Zakynthos it takes place at the Great Friday evening of ‘The Epitafios Lamentation’ service.  This custom is meant to symbolize the Harrowing of Hades or, more specifically, the smashing of the Gates of Hades.  I also note a photo in my Enclyclopedia of World Religions of many ostrich eggs being suspended from the ceilings of Armenian churches to serve as symbols of hope and resurrection. But I do NOT wish to know more about such events.
None of that addresses the actual day called ‘Easter Sunday’ (apart from the Paschal greeting, which I suppose only takes up about 10 seconds of the start of the Easter service.) I wish to know what customs and acts of worship and celebration the various Orthodox groups engage in on that one day.  I know there are lots of events in Holy Week leading up to the climax of resurrection Sunday, but I do not wish to know about the days prior to then. Stack Exchange is full of information about that. Nor do I wish to know anything about the date for Easter and controversies / theologies about that. Again, the site is full of such information.
I only want information from Orthodox Christians on what happens on that one day – the Sunday (of Holy Week) – and that could come from any of the groups within Orthodoxy as they all seem to have unique rituals and customs (Nestorian, Monophysite, West Syrian, Armenian, Coptic and Ethiopian).  I know the Paschal greeting starts that Easter Sunday service, but what happens thereafter?
How do Orthodox Christians celebrate Christ's resurrection on Easter Sunday?
The most obvious and almost universally Orthodox one is that they celebrate Easter on a different date than Churches in the West.
Orthodox and Western churches observe most holidays 13 days apart as they follow the Julian and Gregorian calendars, respectively.
Like the West their liturgical season of Easter ends with the Feast of Pentecost inclusively.
Here follows a sample of some Easter liturgical celebrations:
For Easter, their computations differ based on what dates the first full moon after the spring equinox and Jewish Passover fall in any given year. Accordingly, in some years, their Easter dates coincide, in others they can be weeks apart. The next &quot;joint&quot; Easter observance will be in 2025.
Seeing that there the Orthodox communion consists of 14 autocephalous (that is, administratively completely independent) regional churches, plus the Orthodox Church in America and recently the Orthodox Church of Ukraine; the diverse liturgical celebrations and regional customs would take a entire book to write about. They are quite diverse!
To start with here is a sampling for the liturgical celebrations of Easter:

About Greek Orthodox Easter: Everything You Need to Know
On Holy Saturday, psalms are read and Resurrection hymns are sung, telling of Christ’s descent into Hades: “Today Hades cried out groaning,” the psalm says.
The hymns speak of the conquering of death and the day’s celebration is called “First Resurrection.” Most of the readings of this day are from the Old Testament on the prophecies and promise of the conquering of death.
Finally, at midnight, there is the moment that all Greeks around the world eagerly anticipate: The Resurrection ceremony, when the faithful can finally greet one another by saying “Christos Anesti!” (Christ is risen!).
On this night, Greeks wear their Sunday best, take a white candle, and go to church to attend the liturgy, waiting for midnight.
Children hold their lampatha (λαμπάδα) a decorated white candle given to them by their godfather or godmother. This is a much-anticipated gift by children.
Children keep their lampatha throughout the year because the blessed candle which has been lit by the Holy flame on Resurrection night can be used in other special liturgies such as baptisms and weddings.
At midnight, all the priests come out and chant “Christos Anesti!” while they pass the Holy Light from which all the faithful light their candles and pass the light to one another, saying “Christos Anesti!” with the recipient replying “Alithos Anesti!” or “Truly, He is risen!”
The Holy Fire
In Orthodox tradition, the Holy Fire is considered a miracle that occurs annually on the day preceding Pascha within Jesus Christ’s tomb in the Church of the Holy Sepulchre in the Old City of Jerusalem.
In the church, a blue light is said to emit from within Jesus Christ’s tomb, rising from the marble slab covering the stone believed to be that upon which Jesus’ body was placed for burial.
The light is believed to form a column of fire, from which candles are lit. This fire is then used to light the candles of the clergy and pilgrims in attendance.
The fire is also said to spontaneously light other lamps and candles around the church. Pilgrims and clergy say that the Holy Fire does not burn them.
The Patriarch is inside the chapel kneeling in front of the stone, while the church is dark. Then the Patriarch comes out with the two candles lit and shining brightly in the darkness.
The crowd roars as they witness the bright candles with the Holy Fire and light their own, jubilant after seeing the miracle.
The Holy Fire, which Greeks call Holy Light, is taken to Greece by a special flight, while it is received in the country by political and church leaders with all the honors of a visiting state leader.

Individual Eastern Orthodox Churches have a variety and sometimes varies Eastern customs involving subjects as food to diverse religious practices. It is not uncommon where I live to see Greek Orthodox roasting lamb outside in their back yard.
It is customary among Orthodox Christians to greet one another during the Easter season with the Paschal greeting. The salutation begins with the phrase, &quot;Christ ​is Risen!&quot; The response is &quot;Truly; He is Risen!&quot; The phrase &quot;Christos Anesti&quot; (Greek for &quot;Christ is Risen&quot;) is also the title of a traditional Orthodox Easter hymn sung during Easter services in celebration of Jesus Christ’s resurrection.
In the Orthodox tradition, eggs are a symbol of new life. Early Christians used eggs to symbolize the resurrection of Jesus Christ and the regeneration of believers. At Easter, eggs are dyed red to represent the blood of Jesus that was shed on the cross for the redemption of all men.
One of the most common Christian symbols associated with Easter is the lamb. It is often depicted with a banner that bears a cross, and it is known as the Agnus Dei, meaning &quot;Lamb of God&quot; in Latin.

In Lebanon, many Orthodox Christians attend a church liturgy at Easter, whether it is on Sunday morning or midnight liturgy between Holy Saturday and Easter Sunday. On Easter Sunday, many families hold a special lunch consisting of turkey or chicken stuffed with nuts and served with rice. The afternoon is spent visiting friends and family members. Many homes have maamoul (cookies) on a plate with other delicacies such as chick peas covered with sugar and sweet almonds.
In Bulgaria, many worshippers celebrate outside churches after midnight liturgy, carrying candles to symbolize the resurrection of Jesus Christ. Painted eggs are cracked or smashed and richly-painted Orthodox churches are filled with clouds of incense and choir songs.
In Greece, Easter Sunday is also a widely celebrated occasion. Lambs are roasted on a spit and the provision of wine is abundant. The roasted lamb is served in honor of Jesus Christ, who was sacrificed and rose again on Easter. Lamb is the most traditional Greek Easter food. Red-dyed eggs are cracked against each other and the person with the last remaining uncracked egg will have good luck. Easter Sunday is a time of festivity and people eat, chat or dance throughout the night.
On the island of Crete, many villages prepare for a bonfire effigy of Judas Iscariot, who betrayed Jesus Christ, as described in the New Testament of the Bible. In the lead up to the bonfire event, people gather sticks and branches to prepare to burn the effigy.
Around the world, many Orthodox Catholic Churches, including the Greek and Russian Orthodox churches, hold Easter liturgies during the Easter period according to the Julian calendar. Families unite and join in Orthodox Easter activities, festivities and traditions.


Serbian Orthodox families traditionally begin the feasting after Easter Sunday services. They enjoy appetizers of smoked meats and cheeses, boiled eggs and red wine. The meal consists of chicken noodle or lamb vegetable soup followed by spit-roasted lamb.
Holy Saturday is a day of strict fasting for Russian Orthodox Christians, while families stay busy making preparations for the Easter meal. Usually, the Lenten fast is broken after the midnight mass with traditional Paskha Easter bread cake. - What Is Orthodox Easter?

Special mention should be made about the Holy Fire at Jerusalem.

The Holy Fire is described by Orthodox Christians as a miracle that occurs every year at the Church of the Holy Sepulchre in Jerusalem on Great Saturday, or Holy Saturday, the day preceding Orthodox Easter. However, many dispute the alleged miraculous descent of the Fire.
Orthodox tradition holds that the Holy Fire happens annually on the day preceding Orthodox Pascha (Orthodox Easter). During this time, blue light is said to emit within Jesus Christ's tomb, rising from the marble slab covering the stone bed believed to be that upon which Jesus' body is to have been placed for burial. The marble slab is now in the Church of the Holy Sepulchre in the Old City of Jerusalem. The light is believed to form a column of fire, from which candles are lit. This fire is then used to light the candles of the clergy and pilgrims in attendance. The fire is also said to spontaneously light other lamps and candles around the church. Pilgrims and clergy say that the Holy Fire does not burn them.
While the Patriarch is inside the chapel kneeling in front of the stone, there is darkness but far from silence outside. One hears a rather loud mumbling, and the atmosphere is very tense. When the Patriarch comes out with the two candles lit and shining brightly in the darkness, a roar of jubilation resounds in the Church.
Thousands of pilgrims as well as local Christians of all denominations gather in Jerusalem to partake and witness this annual event.
The Holy Fire is taken to Greece by special flight, and similarly to other Orthodox countries or countries with major Orthodox churches, such as Georgia, Bulgaria, Lebanon, Romania, Egypt, Cyprus, North Macedonia, Serbia, Ukraine and Russia, being received by church and state leaders.
History
The historian Eusebius writes in his Vita Constantini, which dates from around 328, about an interesting occurrence in Jerusalem of Easter in the year 162. When the church wardens were about to fill the lamps to make them ready to celebrate the resurrection of Christ, they suddenly noticed that there was no more oil left to pour in the lamps. Upon this, Bishop Narcissus of Jerusalem ordered the candles to be filled with water. He then told the wardens to ignite them. In front of the eyes of all present every single lamp burned as if filled with pure oil. Christian Orthodox tradition holds that this miracle, which predates the construction of the Holy Sepulchre in the fourth century, is related to the Miracle of the Holy Fire. They admit that the two differ, as the former was a one-time occurrence while the Miracle of the Holy Fire occurs every year. However, they have in common the premise that God has produced fire where there, logically speaking, should have been none.
Around 385 Egeria, a noble woman from Spain, traveled to Palestine. In the account of her journey, she speaks of a ceremony by the Holy Sepulchre of Christ, where a light comes forth (ejicitur) from the small chapel enclosing the tomb, by which the entire church is filled with an infinite light (lumen infinitum).


Holy Fire in 2018
Interesting enough is that Orthodox celebrate a particular celebration during Eastertide known as Mid-Pentecost

Mid-Pentecost or Midfeast, also Meso-Pentecost is a feast day which occurs during the Paschal season in the Eastern Orthodox Church and those Eastern Catholic Churches which follow the Byzantine Rite.
Mid-Pentecost celebrates the midpoint between the Feasts of Pascha (Easter) and Pentecost. Specifically, it falls on the 25th day of Pascha. At the feast of Mid-Pentecost, a Small Blessing of the Waters is traditionally performed after the liturgy of the feast.
Mid-Pentecost is a one-week feast which begins on the 4th Wednesday of Pascha, and continues until the following Wednesday. That is to say, it has an Afterfeast of seven days. Throughout these eight days (including the day of the feast) hymns of Mid-Pentecost are joined to those of the Paschal season. Many of the hymns from the first day of the feast are repeated on the Apodosis (leave-taking of the feast). Although it is ranked as a Feast of the Lord and has an Afterfeast, Mid-Pentecost itself is not considered to be one of the Great Feasts of the church year.