When Shawn Whiting began documenting the protests over George Floyd’s death late last month, he started by posting photos and videos on Twitter and livestreaming marches on the social media service.

But Mr. Whiting, 32, a video game designer in Seattle, quickly decided that Twitter’s video and audio quality wasn’t good enough. So he checked out other sites and settled on Twitch, a platform known for broadcasting video game play.

Now Mr. Whiting streams Seattle’s Black Lives Matter protests every day — sometimes for more than four hours straight — on Twitch, where he gets anywhere from several hundred to several thousand viewers at a time.

“People say, ‘Please don’t stop streaming — you’re the only source’” on the ground, he said. He added that there’s a constant appetite to know what’s going on and “a constant question of, how long can this last?”

Mr. Whiting is one of dozens of people across the United States who have turned to Twitch to bring the movement’s message and actions live to viewers as the marches and sit-ins stretch into a third week.

Some Black Lives Matter protesters and citizen journalists have created Twitch channels just to broadcast the protests, while gamers who were already on the site switched to showing the demonstrations instead of video games. Other Twitch users simultaneously pull together up to 10 protest live streams from places including Nashville and Washington, D.C., into a single feed, so that people can see the action in multiple cities at a glance.

The activity has turned Twitch, which is owned by Amazon, from a site that mostly streams gamers playing hits like League of Legends, Fortnite and Valorant into an unexpected hub of social activism.

“Over the past few weeks, we’ve seen creators livestreaming content from the protests and engaging their communities in open conversations around race, inequality and how to effect change,” said Brielle Villablanca, a Twitch spokeswoman. “Twitch stands firmly against racism in any form, and we wholeheartedly support our community using our service to share what they believe in.”

(The exception, Twitch said, was showing protest content that violates its guidelines because it is extremely violent or contains illegal acts. )

Some streamers said that while they haven’t had any official communication with Twitch about the protests, company employees have privately supported their efforts. Mr. Whiting said a Twitch employee had reached out to him and said, “‘Hey I’ve seen what you’re doing, glad to have you on the platform streaming this sort of coverage. If you need tips, let me know.’”

Twitch, which in many ways is akin to YouTube, has more than seven million different channels and big stars like Fortnite player Turner “Tfue” Tenney. It has long dominated livestreaming of video games. In May, people watched more than 1.7 billion hours of live video on the platform, compared to 939 million hours a year earlier, according to data compiled by Twitch analytics website SullyGnome and provided by StreamElements, a livestreaming services website. Viewers can directly interact with streamers through a chat function.

When the protests over Mr. Floyd’s killing in police custody began, streamers flocked to Twitch to provide lengthy alternatives to what some said were out-of-context video clips from mainstream news outlets.

Many said they chose Twitch because they were familiar with the site from video games and wanted to leverage an existing tech-savvy audience. Twitch also has some technical tools for live broadcasting that other platforms lack, they said, like a robust moderation system to avoid spam in chats.

Natalie Casanova, a longtime streamer, has been broadcasting Los Angeles’s Black Lives Matter protests on her ZombiUnicorn channel on Twitch, which has 220,000 followers. She said Twitch allowed her to advertise a campaign to raise money for the N.A.A.C.P.

“They are used to me speaking up and out about stuff, so my community specifically enjoyed it,” Ms. Casanova, 33, said of her protest coverage. “It moved them.”

Many of the protest streams are found on Twitch’s “Just Chatting” section, which features a category that streamers refer to as “IRL” or “in real life.” Two of the largest protest-focused Twitch channels there are OppositionTV, which was created to cover the events, and WOKE, which had largely been dormant until the demonstrations began.

The WOKE Twitch channel, which is run by streamer Ryan Carmichael, has more than 98,000 followers. For the past few weeks, Mr. Carmichael and his team of about 20 people have compiled and sifted through protest livestreams from around the country. He chooses what he deems to be the most interesting footage and simultaneously broadcasts it. Most of the more than 1,000 streamers WOKE monitors go live on Facebook, YouTube, Twitch or Twitter.

Data provided by Mr. Carmichael, who is based in Lakeland, Fla., showed that his stream attracted more than eight million views between May 28 and June 15. At one point, more than 52,000 people watched at once. As of Monday, WOKE was the most-watched of Twitch’s “Just Chatting” channels over the last 14 days, according to SullyGnome.

On Monday afternoon, WOKE aired three Facebook streams from Louisville, Ky., where one streamer, coughing, said police were using tear gas and pepper bullets. Also visible were two broadcasts from the Capitol Hill Organized Protest in Seattle, a rally in Nashville and two angles of a protest in Washington.

Mr. Carmichael, 34, said he wanted to appeal directly to gamers by aggregating the livestreams on a platform they were already using.

The gaming community has “a white male predominance,” he said. “So I kind of thought that this was the audience that really needed to see not the craziness of it, but the speeches and the talks and the reality of what’s going on.”

OppositionTV is smaller, with 11,000 followers and a 24-hour livestream run by Brett Polvado, a 29-year-old from central Texas who used Twitch in the past to stream video games.

Since Mr. Polvado started compiling protest streams several weeks ago, “I have seen a million of these tiny streams come up, doing exactly what we’re doing,” he said. “Ultimately, the whole goal from me was all eyes on deck.”

One of the streams that the Twitch channels are compiling is from Kon Yi, who has been broadcasting the unrest in Washington on Twitch. Mr. Yi, 37, said he began documenting the protests out of a sense of responsibility to keep people informed. He said he has taken pleasure in showing how the demonstrations have grown more peaceful over time.

“To show the progression to what the protests are now, it’s a story I’m trying to give,” he said. “I think the people are enjoying what they see, versus whatever bias the media might have.”

But as Twitch streamers film the unrest, some have been confronted on the streets and questioned about what they’re doing.

“A lot of people aren’t doing it for the right reasons; they’re just trying to get clout, because there’s such a demand to watch this stuff,” Mr. Yi said.

Mr. Whiting, who also still uses Twitter to stream, has been met with suspicion by some protesters who are concerned he is surveilling them while he streams. He said he feels obligated to keep filming.

”I do feel pressure to continue streaming when there’s more people watching,” Mr. Whiting said, adding that he sometimes stays live until 3 a.m. or 4 a.m. because people beg him not to turn off the camera. “It makes me feel a responsibility to stay out there and keep documenting what’s happening. If something goes totally wrong, there’s no witnesses.”