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An easy-to-use BSB number lookup utility and validator.
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The BSB Gem

A Bank State Branch (BSB) number is a code that identifies banks and branches in Australia. This gem provides an easy-to-use lookup utility and an ActiveModel validator for use in any Rails project.

This gem aims to provide a scalable and developer-friendly solution for BSB lookup and validation. If you are building a financial application targeting Australian customers, properly validating BSB numbers is an essential component of a hassle-free user experience.


Add this line to your application's Gemfile:

gem 'bsb'

And then execute:

$ bundle


BSB Lookup

To lookup a BSB number:

BSB.lookup "012003"

You will get a hash back, including the highly-useful full bank name which can be displayed to the user:

{:bsb=>"012003", :mnemonic=>"ANZ", :bank_name=>"Australia & New Zealand Banking Group Limited", :branch=>"115 Pitt St Sydney", :address=>"115 Pitt St", :suburb=>"Sydney", :state=>"NSW", :postcode=>"2000", :flags=>{:paper=>true, :electronic=>true, :high_value=>true}}

BSB lookup with this gem is extremely performant. A decent MacBook Pro can easily run 100,000 lookups a second.


There's a public method for you to normalise a BSB number from a variety of formats, for example:

> BSB.normalize "083-004"
=> "083004"

> BSB.normalize "06 2000"
=> "062000"

ActiveModel Validator

If you have included this gem in your Rails project, you can use the custom validator bsb_number. For example, in your model:

validates :bsb, :account_number, :account_name, presence: true
validates :bsb, length: { is: 6 }, bsb_number: true

This validator ensures that the BSB number entered by the user actually exists.

Data source

Included in this gem is also a set of Rake tasks to generate the JSON-formatted compressed database for maximum performance (it's only as readable as the offset data files).

Two data sources are used:

  • APCA BSB directory (Updated bi-monthly. This gem will track the changes and push gem updates as frequently as my time allows.)
  • APCA Key to Abbreviations and BSB Number (No regular updates)

Other formats of APCA BSB data is available from


  1. Fork it ( )
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request
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