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Snaps quickstart

Get started creating your own Snap. Use the @metamask/create-snap starter kit to initialize a Snap monorepo project built with TypeScript and React. See the following video demo:

Prerequisites​

Create the project​

Create a new Snap project using the @metamask/create-snap starter kit by running:

yarn create @metamask/snap your-snap-name

or

npx @metamask/create-snap your-snap-name

or

npm create @metamask/snap your-snap-name

See Snaps files to learn about your Snap project files.

Start the Snap​

From the root of the newly created project, install the project dependencies using Yarn:

yarn install

You may get a warning like the following:

@lavamoat/allow-scripts has detected dependencies without configuration. explicit configuration required.
run "allow-scripts auto" to automatically populate the configuration.

You can fix this by running the following command:

yarn run allow-scripts auto

Start the development server:

yarn start

You are now serving the Snap at http://localhost:8080 and its front-end dapp at http://localhost:8000.

Connect to the Snap​

On the front-end dapp, select the Connect button and the MetaMask Flask extension pops up and requires you to approve the Snap's permissions.

Once connected, select the Send message button to display a custom message within a confirmation dialog in MetaMask Flask.

Customize the Snap​

Open the project in a text editor. You can customize your Snap by editing index.ts in the packages/snap/src folder.

index.ts contains an example request that uses the snap_dialog method to display a custom confirmation screen:

index.ts
import type { OnRpcRequestHandler } from "@metamask/snaps-sdk";
import { panel, text } from "@metamask/snaps-sdk";

/**
 * Handle incoming JSON-RPC requests, sent through wallet_invokeSnap.
 *
 * @param args - The request handler arguments as an object.
 * @param args.origin - The origin of the request, e.g., the website that invoked the Snap.
 * @param args.request - A validated JSON-RPC request object.
 * @returns The result of snap_dialog.
 * @throws If the request method is not valid for this Snap.
 */
export const onRpcRequest: OnRpcRequestHandler = async ({
  origin,
  request,
}) => {
  switch (request.method) {
    case "hello":
      return snap.request({
        method: "snap_dialog",
        params: {
          type: "confirmation",
          content: panel([
            text(`Hello, **${origin}**!`),
            text("This custom confirmation is just for display purposes."),
            text(
              "But you can edit the Snap source code to make it do something, if you want to!",
            ),
          ]),
        },
      });
    default:
      throw new Error("Method not found.");
  }
};

Edit the text in any text() component and select the Reconnect button on the front-end to re-install the Snap.

note

MetaMask Flask automatically re-installs locally hosted Snaps whenever it receives a connection request for them.

The next time you select the Send message button, you see the updated text in the confirmation dialog.

You've now successfully connected, installed, interacted with, and customized your Snap!

Next steps​