Why do AI models struggle with online hate speech detection?

Hate speech that once circulated in person now travels farther and faster via anonymous online accounts behind a screen.

As the United Nations marks the International Day for Countering Hate Speech on June 18, UN Secretary-General Antonio Guterres has warned that social platforms are amplifying the threat.

With artificial intelligence (AI) increasingly tasked with detecting and removing hate speech online, Al Jazeera looks at where these systems fall short compared with human judgement.

According to the UN, hate speech covers any communication – spoken, written or behavioural – that discriminates against or incites violence towards a person or group.

The UN states that hate speech targets a person’s actual or perceived identity, race, ethnicity, religion, gender, sexual orientation or disability. And it isn’t limited to words, with the UN noting it can also take the form of images, cartoons, gestures and even objects.

According to a 2023 joint survey of 8,000 people in 16 countries done by polling company Ipsos and the UN Educational, Scientific and Cultural Organization (UNESCO), more than two-thirds of internet users encountered hate speech online.

The survey also found that 33 percent of people thought LGBTQI people experienced the most cases of hate speech, followed by ethnic and racial minorities (28 percent) and women (18 percent).

Meta, which owns Facebook, has removed fewer hateful posts since 2023. In the last quarter of 2025, the company removed 1.3 million posts from Instagram and 1.3 million from Facebook, compared to 7.4 million removed from Instagram and 5.8 million from Facebook in the fourth quarter of 2024.