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Chat Format Converter

Convert conversation histories between the OpenAI Chat Completions, Anthropic Messages and Gemini request formats — including system prompts, images, tool calls and tool results.

Runs locally — your input never leaves this page.

Source format
Convert to

    How to use

    1. Paste a messages array or a full request body. The source format is detected automatically.
    2. Choose the target: OpenAI, Anthropic or Gemini.
    3. The system prompt is moved to the right place, images and tool calls are rewritten, and tool results are matched to their calls. Notes explain anything that needed adjusting.

    FAQ

    What are the main differences between the formats?

    OpenAI puts the system prompt in a system message and tool results in separate tool messages. Anthropic uses a top-level system field, requires user and assistant turns to alternate, and puts tool_result blocks inside user messages. Gemini uses contents with user/model roles, parts, and functionCall / functionResponse.

    Are image URLs supported everywhere?

    Base64 images convert cleanly between all three formats. Remote image URLs map to image_url (OpenAI) and URL sources (Anthropic), but Gemini expects uploaded files or Cloud Storage URIs in fileData, so you may need to upload the image first.

    Report a bug or suggest a feature →