Compare two prompts and get an evaluation checklist.
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Plugsky is OpenAI-compatible with flat-rate plans — see pricing or start on the free plan (2 free models, no card).
The Prompt Diff and Evaluator is a browser page for comparing prompt variants side by side and judging which one produces better responses for a given task. It is aimed at prompt engineers and product teams iterating on instructions who want a structured comparison instead of ad-hoc edits. The page frames the evaluation workflow: define the task, run both prompts on identical inputs and score the outputs against explicit criteria. Subjective quality still needs human review.
One thing at a time: a system instruction, an example, a format rule or a sampling setting. Changing several at once makes it impossible to tell which edit caused the difference.
Use a short rubric covering correctness, format adherence, tone and length, plus practical measures such as latency and token cost. Score the same inputs for both prompts before comparing.
It can help triage large batches, but models carry position and verbosity biases. Use automated scoring as a first pass and keep human review for subjective or high-stakes output.
Canonical pricing and plans: plugsky.com/#sec-pricing · Terms · SLA · Docs