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Original author(s)Neil Fraser, Quynh Neutron, Ellen Spertus, Mark Friedman
Developer(s)Google, MIT
Initial releaseMay 2012; 11 years ago (2012-05)
Stable release
Q1 2022 Patch 3 / 8 June 2022; 18 months ago (2022-06-08)[1]
Written inJavaScript
PlatformWeb browser
Size150 KB
Available in50 languages
List of languages
LicenseApache License 2.0

Blockly is a client-side library for the programming language JavaScript for creating block-based visual programming languages (VPLs) and editors. A project of Google, it is free and open-source software released under the Apache License 2.0.[2] It typically runs in a web browser, and visually resembles the language Scratch.

Blockly uses visual blocks that link together to make writing code easier, and can generate code in JavaScript, Lua, Dart, Python, or PHP. It can also be customized to generate code in any textual programming language.[3]


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.[4] Neil Fraser began the project with Quynh Neutron, Ellen Spertus, and Mark Friedman as contributors.

User interface

The default graphical user interface (GUI) of the Blockly editor consists of a toolbox, which holds available blocks, and where a user can select blocks, and a workspace, where a user can drag and drop and rearrange blocks. The workspace also includes, by default, zoom icons, and a trashcan to delete blocks.[5] The editor can be modified easily to customize and limit the available editing features and blocks.


Blockly includes a set of visual blocks for common operations, and can be customized by adding more blocks. New blocks require a block definition and a generator. The definition describes the block's appearance (user interface) and the generator describes the block's translation to executable code. Definitions and generators can be written in JavaScript, or using a visual set of blocks, the Block Factory, which allows new blocks to be described using extant visual blocks; the intent is to make creating new blocks easier.


Blockly is used in several notable projects, including:



  1. ^ "Release Q1 2022 Patch 3 · google/Blockly". GitHub.
  2. ^ Metz, Cade. "Google Blockly Lets You Hack With No Keyboard". Wired.
  3. ^ "Google's Blockly Teaches You to Create Apps". NBC Bay Area.
  4. ^ "Google Groups". Retrieved 16 January 2018.
  5. ^ Black, Lucy (12 June 2012). "Google Blockly – A Graphical Language with a Difference". I-programmer. Retrieved 3 July 2019.
  6. ^ "Scratch 3.0's new programming blocks, built on Blockly". Google.
  7. ^ "MIT App Inventor 2". MIT.
  8. ^ "Translate".
  9. ^ "Microsoft MakeCode". Microsoft.
  10. ^ "Microsoft MakeCode Computer Science Education". Microsoft.
  11. ^ "PICAXE Blockly". PICAXE. Retrieved 5 July 2020.
  12. ^ "SAM Labs Blocks: Getting started on Workbench". Retrieved 2020-10-10.
  13. ^ "Blockly Demo: Code". Retrieved 16 January 2018.
  14. ^ "Blockly Demo: JS-Interpreter". Blockly Samples. Retrieved 24 February 2023.
  15. ^ "Localisation statistics for the Blockly core module". Retrieved 16 January 2018.
  16. ^ "Blockly Demo: RTL". Blockly Samples. Retrieved 24 February 2023.