Comparison
Online Evaluation vs Reference-Free Evaluation
Online Evaluation and Reference-Free Evaluation are both common AI/LLM terms but cover different ideas. Here is a quick side-by-side.
When you would reach for Online Evaluation
After offline eval is solid and you have meaningful production volume. Stretch your eval coverage from a fixed set to a live one.
Phoenix running a faithfulness eval on 5% of production RAG traces, dashboard charts the rolling 7-day mean.
When you would reach for Reference-Free Evaluation
When ground truth is impractical to collect or open-ended outputs make exact-match meaningless — most production LLM evaluation.
A faithfulness eval: judge model reads retrieved context + the generated answer, scores whether every claim is supported.
Frequently asked
What is the difference between Online Evaluation and Reference-Free Evaluation?
Online Evaluation: Online evaluation runs scoring functions over live production traffic — usually a sample of recent traces — to monitor quality continuously instead of relying solely on a fixed offline dataset. Reference-Free Evaluation: Reference-free evaluation grades an output without a ground-truth answer to compare against — using rubric-based LLM-as-judge, self-consistency, or property checks like "is the answer grounded in the retrieved context?"
When should I use Online Evaluation vs Reference-Free Evaluation?
After offline eval is solid and you have meaningful production volume. Stretch your eval coverage from a fixed set to a live one. When ground truth is impractical to collect or open-ended outputs make exact-match meaningless — most production LLM evaluation.
Are Online Evaluation and Reference-Free Evaluation the same thing?
No. Online Evaluation is evaluation; Reference-Free Evaluation is evaluation. They are related but address different parts of the AI stack.