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Blockly is a library for building visual programming editors. Try it:

For more complex Blockly installations, including ones that generate code or may be used for education, see our page of examples.


  • Web-based, no Flash.
  • 100% client-side.
  • Only 150 KB compressed.
  • Chrome, Firefox, Safari, Opera, IE.
  • Android and iOS support.
  • Variables, functions, arrays...
  • Syntax errors are impossible.
  • Basic type checking.
  • Extend with custom blocks.
  • Open source.
  • Export as JS, Python, and more.
  • Clean code generation.
  • Execute code step-by-step.
  • Translated to 40+ languages.
  • RTL for Arabic and Hebrew.

Each of these optional features can be experimented with on the page of demos.


Play with some of the examples to get a feel for Blockly.


Get the code and install it into your application.

Custom Blocks

Make some custom blocks for your application's API.


Get help and show your application to other developers.