App users in the UK and US are spending more time on TikTok than on YouTube, a new report suggests.
Data from app monitoring firm App Annie indicates that average time per user spent on the apps is higher for TikTok, indicating high levels of engagement.
App Annie characterised TikTok as having "upended the streaming and social landscape".
However, YouTube retains the top spot for overall time spent - not per user - as it has many more users overall.
The Google-owned video giant has an estimated two billion monthly users, while TikTok's most recent public figures suggested it had about 700 million in mid-2020.
App Annie specialises in analysis of the apps market.
The "time spent" metric in its report only accounts for Android phones - but also does not include China, where TikTok - known locally as Douyin - is a major app.
"YouTube still leads TikTok in overall time spent, including in the UK," explained Jamie MacEwan, from Enders Analysis.
"YouTube's mass audience means it's getting more demographics that are comparatively light internet users... it's just reaching everyone who's online."
The most-invested YouTube users probably "match or surpass" the engagement of TikTokers, he said.
But "none of that's to say TikTok isn't a success", he added.
"TikTok was spending big to attract users, but they were not necessarily hanging around for long compared to other social media," he said.
"Now we know that in the US and UK, TikTok has overhauled YouTube, and is reeling in Facebook... that's a huge seal of approval."
The "time spent" metric in App Annie's report only accounts for Android phones - but also does not include China, where TikTok - known locally as Douyin - is a major app.
It shows that in the UK, TikTok surpassed YouTube back in June 2020, and has maintained its lead since. In the US, TikTok and YouTube traded places multiple times late last year before TikTok emerged on top in April 2021.
Other metrics tracked by the firm reflect TikTok's increasing importance.
Among social, communication, photo, video and entertainment apps, TikTok is ranked as the most-downloaded worldwide since 2020. It also competes with YouTube for the top spot in consumer spending since last year.
App Annie's report also suggests that apps with live-streaming - including TikTok - are fuelling a surge in money spent on creators.
Apps that have live-streaming as "a prominent feature" accounted for three-quarters of money spent in the top 25 social apps in the first half of 2021, the report says.
On gaming site Twitch, for example, viewers can purchase "Bits" - a virtual currency - and spend them to "cheer" streamers during a live stream. Or they can set up a recurring subscription to a creator's channel in exchange for subscriber-only benefits.
Tiktok lets users tip creators with "coins" - its own version of "bits", while YouTube runs similar programmes for its live streams.
"Live-streaming is driving growth in engagement for social apps, which sets them up for consumer spend," App Annie says.
The report also highlights another winner in the past year - Snapchat.
The augmented-reality focused messaging app saw its downloads outside the US grow by nearly 30% year-on-year, and by 45% on two years ago, App Annie's data suggests.