Variables and Secrets

Last updated Jan 28, 2026

Bindings

Variables and secrets are bound as follows:

const mf = new Miniflare({
    bindings: {
        KEY1: "value1",
        KEY2: "value2",
    },
});

Text and Data Blobs

Text and data blobs can be loaded from files. File contents will be read and bound as strings and ArrayBuffers respectively.

const mf = new Miniflare({
    textBlobBindings: { TEXT: "text.txt" },
    dataBlobBindings: { DATA: "data.bin" },
});

Globals

Injecting arbitrary globals is not supported by workerd ↗︎. If you're using a service Worker, bindings will be injected as globals, but these must be JSON-serializable.

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description: "Miniflare will always upgrade Web Socket connections. The Worker must respond\nwith a status 101 Switching Protocols response including a webSocket. For\nexample, the Worker below implements an echo WebSocket server:" title: WebSockets image: https://developers.cloudflare.com/workers/testing/miniflare/core/web-sockets/og.png?v=49b51a22cdccba75

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