Chatbot Arena
Also known as: LMSYS Arena, LMArena
Crowdsourced blind A/B comparisons of LLM responses, aggregated into an Elo leaderboard.
A crowdsourced LLM evaluation platform where humans pick between two anonymized model responses to the same prompt. Pairwise outcomes are aggregated into an Elo rating that ranks models by perceived quality.
In practice
Most-cited human-preference leaderboard. Expect questions on its bias (style preference, prompt distribution) and why model trainers chase it.
Related topics
Related terms
Hallucination
When a model confidently makes up something that isn't true.
LLM Evaluation
Measuring whether an LLM does what you want, beyond "looks fine to me".
Perplexity
Exp(average cross-entropy) on held-out text; lower means the model is less surprised by real data.
Reasoning Model
An LLM trained to reason at length internally before answering. Slower and more expensive, but much better on hard problems.
Guardrails
Pre- and post-processing layers that block bad inputs/outputs and enforce policy on top of an LLM.
MMLU (Massive Multitask Language Understanding)
Multiple-choice benchmark across 57 academic subjects; the standard "raw knowledge" headline number.