One in eight porn videos promoted to first-time users of the UK's leading adult sites are labelled with text describing sexually violent acts, according to a study.
It analysed titles and descriptions of 131,738 videos on Pornhub, XVideos and XHamster's launch pages.
One researcher said the prevalence of descriptions of rape, physical abuse and incest was "shocking".
The sites have challenged the study and said they remove illegal content.
The findings are published in the latest issue of The British Journal of Criminology, and were first reported by the Sunday Times.
The researchers involved took hourly screenshots of the homepages on the three most popular porn websites, over a six-month period between 2017 and 2018.
Descriptions and titles - but not the content of the videos themselves - were searched-for keywords that corresponded with the World Health Organisation’s definition of sexual violence.
The researchers then excluded what they considered to be consensual BDSM (bondage, domination and sado-masochism) videos from their findings.
The research reported:
- more than 8,000 titles referred to physical aggression or forced sexual activity
- 2,966 titles described image-based sexual abuse, including “hidden cams” and “upskirting”
- 5,785 titles described sexual activity between family members - the most common category of “sexually violent” material identified in the report
Pornhub, XHamster and XVideos were chosen as they are the three most visited porn websites in the UK.
The content would be visible to first-time visitors on the website, and was available to view for free with little or no age verification process, the study said.
Common keywords included “forced”, “grope” and “molest,” the analysis found.
The word “teen” was the most frequently appearing word in the entire data, accounting for 7.7% of all videos.
This rose to 8.5% in videos which were identified as having described sexual violence.
Terms and conditions
In their terms and conditions, Pornhub and XVideos prohibit all content “depicting” child sexual abuse, rape, incest and forced sexual acts.
And XHamster bans material that is “unlawful, threatening, abusive, harassing” or “hateful”.
Pornhub's owner Mindgeek recently removed millions of videos that had been uploaded by users who had not been verified after claims of hosting illegal content.
But it defended the clips it has allowed to remain online.
“Consenting adults are entitled to their own sexual preferences, as long as they are legal and consensual, and all kinks that meet these criteria are welcome on Pornhub,” said a spokesman.
The other sites did not respond to the BBC's request for comment.
Last week, Pornhub released its first-ever transparency report, which said it had removed 653,465 videos for violating its rules.
"Remember, a kink that looks degrading or humiliating is not the same thing as an illegal, abusive, or non-consensual act," the report added.
"What goes on between consenting adults is exactly that: consensual. Non-consent must be distinguished from consent to relinquish control."
But Clare McGlynn QC, a professor of law at Durham who co-authored the study, told the Sunday Times: “It’s shocking that this is the material that the porn companies themselves are choosing to showcase to first-time users."
Fiona Vera-Gray, a legal research fellow and co-author of the study, added that sexually violent material “eroticised non-consent” and distorted “the boundary between sexual pleasure and sexual violence”.
The wording used in titles and descriptions are optimised for searches “to entice an audience,” said Charlotte Rose, a former sex worker of more than 20 years.
She said the majority of porn produced in the UK was “ethical and consensual” but that videos on leading platforms were not always transparent.
“For your average viewer it can be hard to tell what is real and what is fantasy,” she explained.
“Porn performers can make things look convincing, they can depict harm but actually, the actors are enjoying it because that’s their kink.”
Ms Rose said some extreme and unregulated porn “can create a bridge that leads to other violent acts” and argued that viewers should be “made aware” of porn videos that are “ethical, consensual and fantasy, not real life”.
If you, or someone you know, have been affected by sexual abuse or violence, this page might be able to help.