Jeff Bezos shot straight to the top of a ranking of America's biggest donors - here's how much tech moguls gave away to good causes in 2018

The former Twitter CEO and founder of blog platform Medium donated $100 million to various youth and educational charities.

Sandberg plugged $100 million into her donor-advised fund in 2018, which will reportedly continue to support LeanIn.org, her initiative to further female leadership, and OptionB.org, a website founded by Sandberg which helps people cope with grief.

According to the Chronicle of Philanthropy, Sandberg also seeded a new fund late last year called the Goldberg Charitable Support Fund, although it's not yet clear what this fund will support.

Bill and Melinda Gates published their annual letter on Tuesday, detailing what they've learned about and invested in over the past year.

Read more: Bill and Melinda Gates revealed their 9 biggest surprises from 2018 in a letter dedicated to Microsoft's late cofounder

They gave $138 million to philanthropic causes in 2018, plugging money into global health, education, and advocacy projects, according to the Chronicle.

Last year, the couple topped the Philanthropy 50 list with donations of almost $5 billion in 2017.

Mark Zuckerberg and Priscilla Chan funnelled more than 1.4 million Facebook shares into their philanthropic fund last year, meaning an overall spend of $214 million. It was a significant reduction on the $2 billion they gave to good causes in 2017.

Microsoft cofounder Paul Allen passed away in October 2018 after donating $261 million to charity.

He primarily gave his money to medical and AI organisations, while also donating to museums including the Flying Heritage and Combat Armor Museum, the US Olympic and Paralympic Foundation, and the Museum of Pop Culture.

Read more: The extraordinary life of Microsoft's billionaire cofounder Paul Allen, who has died at the age of 65

Former Microsoft CEO Steve Ballmer and his wife Connie gave away $295 million to philanthropic causes in 2018. It is the first time they have appeared in the Chronicle's ranking since 2014, when they gave away $110,000.

eBay founder Pierre Omidyar and his wife Pam gave away $392 million in 2018 to a range of causes, up $135 million in 2017.

Jeff and his soon-to-be-ex-wife Mackenzie Bezos were new entrants to the Chronicle of Philanthropy list — and they went straight in at number one overall.

The pair donated $2 billion to good causes. In June 2018, Bezos — who is the world's richest man — asked Twitter what philanthropic cause he should give his billions to.

In the end, the money was used to fund non-profit schools and homeless charities through Bezos' "Day One Fund."