Prompt Optimizer is an open-source application for improving, testing, comparing, and managing prompts for language and image-generation models. Users can start with a manually written prompt, a template, an imported prompt, or a community source and use AI-assisted optimization to turn it into a more explicit and reusable instruction.

The application supports system- and user-prompt optimization, iterative refinement, side-by-side evaluation, multi-turn testing, variables, function calling, and many model providers. It also includes prompt favorites with version history and source metadata, plus image workflows such as text-to-image, image-to-image, multi-image generation, and style transfer. The software is available as a web app, desktop app, Chrome extension, Docker deployment, and MCP-compatible service.

Prompt Optimizer is aimed at users who want prompt engineering to be a repeatable workflow rather than trial and error in a chat window. Its client-side architecture can communicate directly with configured AI providers, and its testing and asset-management features make it useful for maintaining prompt libraries used across applications, teams, and different model families.