Mark Kearns, 38, a web designer and gamer from Chicago, stumbled upon a new video game called Star Citizen while online in late 2013. The game, which was in development, promised to revive the spaceflight simulation genre with a sprawling universe for players to explore.

Intrigued, Mr. Kearns decided to pledge money to see the game come to fruition. In total, he donated $175, which gained him access to Star Citizen’s alpha version — a playable version of the game in its early stages — plus a virtual ship to use in the game.

Mr. Kearns and others have now vaulted Star Citizen into the record books. Since 2013, the game has quietly amassed more than $148 million in funding — all from regular people who have donated either through the crowdfunding site Kickstarter or through the game’s online donations page. The amount is a record for a crowdfunded video game, and one of the largest for any crowdfunded project. Star Citizen’s developer, Cloud Imperium Games, has not taken any money from traditional financiers.

“My expectation was that we’d raise around $4 million,” said Chris Roberts, 48, the founder of Cloud Imperium Games. “I had investors lined up to help with the rest but Sandy, my wife, told me not to worry about investors — that we’d make it to $20 million. I told her she was crazy, and then it kind of went from there.”