Jolt

transformer.json

{
    "@items": "#valueOf($.order.items)",
    "customer": "#valueOf($.order.customer.name)->#toUpperCase()",
    "total": "@items->#sum(@x: @x.price * @x.quantity)",
    "#foreach(@x in @items) into 'lines'": [
        { "sku": "@x.sku", "qty": "@x.quantity" }
    ]
}

Methods and pipes

Over 80 built-in methods, chainable with -> so a transform reads left to right.

Your C#, callable

Mark a method with [JoltExternalMethod] and call it from any transformer, lambdas included.

Pattern matching

Branch on the shape of your data with #match, type patterns, array and object patterns.

Validated before it runs

Validate() reports syntax and structure issues with exact spans — the same engine behind the VS Code extension.

Where to next

Install the packagesNewtonsoft or System.Text.Json, .NET Standard 2.0 through .NET 10.

Language guideExpressions, variables, loops, lambdas, statements and matching.

Host integrationRegister external methods, compose transformers, stream documents.

VS Code extensionSyntax coloring, completions, hover docs and live validation.