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Blockly is one of the libraries used to create the blocks of Scratch 3.0. It was developed by Google and MIT.


Blockly is a JavaScript library that allows developers to add a visual code editor to websites and mobile apps. It is also what Scratch Blocks is based on.

Blockly is a library that adds a visual code editor to web and mobile apps. The Blockly editor uses interlocking, graphical blocks to represent code concepts like variables, logical expressions, loops, and more. It allows users to apply programming principles without having to worry about syntax or the intimidation of a blinking cursor on the command line.

– Blockly Website[1]


Blockly development began in Summer 2011. The first public release was in May 2012 at Maker Faire. Blockly was originally designed as a replacement for OpenBlocks in App Inventor.


  • Web-based using Scalable Vector Graphics (SVG)
  • Does not rely on Flash
  • Completely client-side JavaScript
  • Compatible with all major browsers: Chrome, Firefox, Safari, Opera, and IE.
  • Highly customizable and extensible.
  • Can export blocks to many programming languages
  • Support of major web browsers including Chrome, Firefox, Safari, Opera, Internet Explorer
  • Mobile support on Android and iOS
  • Support for variables, functions, and arrays
  • Minimal type checking supported, designed for weakly typed languages
  • Easy to extend with custom blocks. Use the Block Factory to make new blocks
  • Clean code generation
  • Step-by-step code execution for tracing and debugging code
  • Localized into 50+ languages
  • Support for left-to-right and right-to-left languages


As Blockly is open-source, many other programs such as App Inventor 2 and uses it.[2]

External Links


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