The Challenges of AI in Detecting Online Hate Speech

The Rise of Online Hate Speech

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.

Defining Hate Speech

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.

The Prevalence of Online Hate Speech

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.

AI Models Detect Hate Speech Differently

To detect and combat the spread of hate speech online, social media companies have increasingly turned to AI, using content moderation systems powered by large language models (LLMs) that promise to automate content filtering across huge volumes of messages. However, a 2025 study by researchers at the University of Pennsylvania found that these models vary widely in how they identify and classify hate speech, with significant inconsistencies across systems and demographic groups.

The Limitations of AI Hate Speech Detection

While AI systems are able to detect explicit hate speech – for example, when profanities and slurs are used against a particular group – more nuanced examples are missed by LLMs. “One challenging example is the case of implicit hate speech, which is often not detected as such because it contains no mention of slurs,” Arkaitz Zubiaga, an associate professor at Queen Mary University of London, and co-lead of the university’s Social Data Science lab, told Al Jazeera.