An Ishikawa diagram — also called a fishbone diagram or cause-and-effect diagram — places a problem at the right-hand 'head' of a fish skeleton and arranges the contributing causes along the 'bones'. Top-level causes branch off the central spine; sub-causes branch off those, creating a layered picture of why something happened.

Ishikawa diagrams are used in quality improvement, problem analysis, and planning. They help identify all the possible reasons behind a problem or outcome, making them useful far beyond manufacturing — for diagnosing why a blog post underperformed, why an event went wrong, or why a recipe did not turn out as expected.

This diagram type is experimental and requires Mermaid v11.12 or later.

ishikawa-beta
    Poor Recipe Results
    Ingredients
        Wrong quantities measured
        Substitutes used
        Out-of-date produce
    Equipment
        OVEN
            Temperature not calibrated
            Door seal worn
        UTENSILS
            Wrong tin size
            Blunt knife
    Technique
        Steps skipped
        Timings not followed
    Environment
        Kitchen too humid
        Ingredients too cold

The first line is the problem or outcome. Each subsequent category (indented once) becomes a bone; sub-causes are indented further. Sub-groups can be given bold headings (written in capitals) to organise their causes visually.