Offline Prompt Tester

About

Offline Prompt Tester lets you stress-test your LLM prompts by generating variations — rephrased, simplified, formalized, or completely restructured — entirely on your own machine. No cloud. No API keys. No data leaves your device.

Connect it to any locally-running LLM (Ollama, Jan.ai, LM Studio, or any OpenAI-compatible endpoint) and see how your prompts hold up when reworded.

Free — no account needed

• 4 perturbation types: Rephrase, Simplify, Formalize, Informalize
• Compare up to 3 types side by side
• Text similarity scoring (Levenshtein)
• Word-level diff view (highlights exactly what changed)
• Token count estimate per result
• Pin your best results across sessions
• Export results as .txt, .csv, or .pdf
• Prompt library (save up to 5 prompts)
• 7-day history
• Right-click any text on any page → "Test this prompt"
• Omnibox shortcut: type pt <your prompt> in the address bar
• Auto-detects available models from your local server
• 10 free tests per day

Pro — one-time purchase, lifetime license

• Unlimited tests per day
• 9 additional perturbation types: Add/Remove Ambiguity, Change Perspective, Reverse Polarity, Add/Remove Constraints, Domain Shift, Role Injection, Adversarial
AI similarity scoring and sentiment delta (via your local LLM)
• Batch mode: run a perturbation across multiple saved prompts at once, with CSV export
• Save up to 50 prompts
• 30-day history