Moderating Harm: Benchmarking Large Language Models for Cyberbullying Detection in YouTube Comments

TL;DR

This study benchmarks three large language models for detecting cyberbullying in YouTube comments across multiple languages, revealing their strengths and weaknesses to improve moderation tools.

Contribution

It provides a comprehensive comparison of GPT-4.1, Gemini 1.5 Pro, and Claude 3 Opus on multilingual cyberbullying detection, including a publicly available dataset and prompts.

Findings

GPT-4.1 achieved the highest F1 score of 0.863.

Gemini had the highest recall of 0.875 but lower precision.

Claude had the highest precision of 0.920 and lowest false positives.

Abstract

As online platforms grow, comment sections increasingly host harassment that undermines user experience and well-being. This study benchmarks three leading large language models, OpenAI GPT-4.1, Google Gemini 1.5 Pro, and Anthropic Claude 3 Opus, on a corpus of 5,080 YouTube comments sampled from high-abuse threads in gaming, lifestyle, food vlog, and music channels. The dataset comprises 1,334 harmful and 3,746 non-harmful messages in English, Arabic, and Indonesian, annotated independently by two reviewers with substantial agreement (Cohen's kappa = 0.83). Using a unified prompt and deterministic settings, GPT-4.1 achieved the best overall balance with an F1 score of 0.863, precision of 0.887, and recall of 0.841. Gemini flagged the highest share of harmful posts (recall = 0.875) but its precision fell to 0.767 due to frequent false positives. Claude delivered the highest precision at 0.920 and the lowest false-positive rate of 0.022, yet its recall dropped to 0.720. Qualitative analysis showed that all three models struggle with sarcasm, coded insults, and mixed-language slang. These results underscore the need for moderation pipelines that combine complementary models, incorporate conversational context, and fine-tune for under-represented languages and implicit abuse. A de-identified version of the dataset and full prompts is publicly released to promote reproducibility and further progress in automated content moderation.