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Although only the Scratch Team makes extensions for the Scratch website, anyone can make experimental extensions for ScratchX. This is a tutorial for making extensions.

  1. Create a JavaScript file on a computer, and add the content
(function(ext) {
    // Cleanup function when the extension is unloaded
    ext._shutdown = function() {};

    // Status reporting code
    // Use this to report missing hardware, plugin or unsupported browser
    ext._getStatus = function() {
        return {status: 2, msg: 'Ready'};

    // Block and block menu descriptions
    var descriptor = {
        blocks: [

    // Register the extension
    ScratchExtensions.register('Sample extension', descriptor, ext);
  1. At the bottom, replace "Sample Extension" with the name of the extension
  2. Add a block. Blocks go in the block array on line 13. Block code looks like this:

['block type','block content','block function name'] This contains 3 things to fill in: block type: The type of block. Types are

Block Type Value
Stack (one space)
Waiting Stack W
Reporter r
Waiting Reporter R
Hat h
Boolean b

block content: Type in the text of the block Use %s for string inputs and %n for number inputs. block function name The name of the function for your block, in the ext object.

For more help making extensions, see the extension documentation