Australia postcode validator
How the postcode format works
- Format
- 4 digits
- Example
- 2000
Things to watch for
- Format-only check — does not confirm the postcode actually exists
- Always exactly 4 digits; the leading digit broadly indicates the state or territory
^[0-9]{4}$An Australian postcode is the 4-digit code Australia Post uses to route mail to a suburb or a group of delivery points, for example 2000 for central Sydney. Anyone validating a shipping address, a checkout form, or a spreadsheet of Australian customer records needs the postcode to be the right length before it’s trusted downstream — especially since Australian postcodes are shared across suburb names in a way that makes the digits, not the suburb spelling, the more reliable field to check first.
A dropped digit or an extra character is the easiest mistake to make and the easiest to catch: a 3-digit or 5-digit string is never a valid Australian postcode, regardless of what suburb name sits next to it on the form.
How this validator works
This tool checks that the input is exactly 4 digits with no letters, spaces, or punctuation, entirely in your browser — nothing is sent to a server, and there’s no signup.
What a pass doesn’t tell you
An Australian postcode carries no check digit, so confirming it’s 4 digits long is the most a client-side tool can do — not that Australia Post has assigned it to the suburb typed alongside it, or that the postcode is currently in use. Confirming either requires Australia Post’s own postcode lookup.
Scope: this page and tool cover postcode format validation only — not suburb matching, address lookup, or delivery confirmation.
postcode FAQ
Does the first digit of an Australian postcode tell you the state?
Broadly, yes. Australia Post groups postcodes so the leading digit lines up roughly with a state or territory — for example codes starting with 3 are Victorian, and 6 is Western Australia — though a few ranges (like the ACT and parts of the Northern Territory) don't map to a single clean digit. It's a useful hint, not a rule this format check can enforce.
Why is an Australian postcode only 4 digits when other countries use 5 or 6?
Australia Post simply designed the system around a smaller population spread across a small number of major postal zones, so 4 digits gives enough combinations to cover every suburb and delivery area without needing a longer code.
Does a correctly formatted postcode mean it actually exists?
No. This tool only confirms the string is exactly 4 digits — it doesn't check the postcode against Australia Post's actual suburb list. Confirming a postcode is real and matches a given suburb requires Australia Post's own postcode lookup.