Bilateral talks between world leaders were the main order of business in Osaka amid a host of simmering tensions on trade and climate change. DW breaks down the most important takeaways from the first day of the summit.
More is at stake during this year's G20 summit than most others in many years. Here's a roundup of what went down on Friday:
Who is hosting and what do they want?
Japan is hosting leaders from the world's top 20 economies in the western city of Osaka. Japanese Prime Minister Shinzo Abe appealed for unity among the sparring leaders, and urged a strong message in support of free trade. Japan will also be keeping close tabs on progress in reviving denuclearization talks with North Korea.
Trump appeared to take Abe's appeal for unity to heart, as he toned down his usually derisive rhetoric and did a three-way fist bump with the Japanese leader and Indian Prime Minister Narendra Modi.
What does the G20 mean for locals?
In stark contrast to the past two G20 summits, which saw massive protests and sometimes violent clashes erupt in the prior host cities of Buenos Aires and Hamburg, the streets in Osaka have been calm, and patrolled by some 30,000 police officers.
Takashi Hatanaka, an employee at a hotel where G20 participants are staying, told DW's Bernd Riegert that the cordoned-off streets don't bother him.
"The guests are welcome. Japan can show that it is taking on responsibility in the world," he said.
What's the main focus of day 1?
Bilateral meetings took center stage on Friday, with world leaders moving through a breakneck schedule of sometimes tense talks with their counterparts. Leaders then came back together for a dinner to round off the day, before they reconvene on Saturday to try to reach an accord.
What were the biggest one-on-one meetings?
Much of the focus on Friday was on US President Donald Trump's talks with Russian President Vladimir Putin, amid tensions over a myriad of issues including Moscow's interference in US elections. It was the first time the two leaders sat together since their first meeting last year in Helsinki, Sweden.
At one point, a reporter asked Trump if he would tell Russia not to meddle in the upcoming US presidential election in 2020. The US leader then turned to Putin with a smile and said: "Don't meddle in the election, please."
After the meeting, Putin's spokesman, Dmitry Peskov, said that Trump reacted positively to an invitation from Putin to attend festivities in Moscow next year marking the 75th anniversary of the US and Russia's World War II victory in Europe.
Outgoing UK Prime Minister Theresa May appeared to have a less friendly reception for Putin for their first meeting since the poisoning of former Russian spy Sergei Skripal in Salisbury, which London has blamed on Moscow.
What are the biggest bones of contention?
The escalating trade war between the US and China has been overshadowing the summit, with world leaders concerned about the impact the rift between the world's top two economies is having on global markets.
All eyes will be on Trump and Chinese President Xi Jinping when they meet for talks on Saturday. Experts told DW that rather than making progress towards a solution, the two are more likely to agree to a truce, which could extend uncertainty.
Besides trade, climate change is the second major sticking point at the summit, with Trump and Brazilian President Jair Bolsonaro uniting to push for nonbinding statements about efforts to address the crisis in the final summit communique.
Escalating tensions between Iran and the US also permeated the talks. European leaders are trying to salvage the 2015 nuclear deal before Tehran makes good on a threat to exceed the maximum amount of enriched uranium it is allowed under the deal, which Trump pulled out of last year.
Who's making trouble?
Putin caused a stir ahead of the summit with an interview he gave to the Financial Times, during which he derided Western liberal values by saying they are "obsolete." He also said German Chancellor Angela Merkel made a "cardinal mistake" by welcoming refugees and migrants into Germany in 2015.
European Council President Donald Tusk fired back, saying Europeans should "firmly and unequivocally defend and promote liberal democracy."
"What I find really obsolete are authoritarianism, personality cults, the rule of oligarchs, even if sometimes they may seem effective," he said.
What is Angela Merkel up to?
The German chancellor also had a packed schedule of meetings with world leaders, including India's Modi and China's Xi, as well as Trump.
Following their meeting, the US leader said Merkel was "a fantastic person, a fantastic woman." Just two days earlier, he'd called Germany "delinquent" for not spending enough on defense for NATO.
Merkel held brief talks with French President Emmanuel Macron at the start of the summit amid ongoing discussions over who will become the next European Commission president.
Merkel also appeared to be feeling well on the first day of the summit, which came a day after the chancellor was shaking and unsteady during a public event in Berlin for the second time within two weeks.
Additional reporting contributed from Osaka by DW's Bernd Riegert.
rs/msh (AP, AFP, dpa, Reuters)