Eircode Routing Key​s in Ireland

What is an Eircode routing key?

The first three characters of an Eircode make up what’s called the routing key. Routing keys were introduced as part of the Eircode system to help with mail sorting and delivery. They are linked to post towns in Ireland’s mail distribution network, based on a hub-and-spoke sorting model used by An Post.

In County Dublin, the routing keys D01 through D24 are based on the historic Dublin postal districts that many of us are familiar with—such as D01 for Dublin 1 or D14 for Dublin 14 (these codes were in public use before Eircode). Outside Dublin, where postal districts were not in public use, brand new routing keys were introduced for each designated post town. This provided national coverage for the routing key system, even if the codes themselves had no prior public association.

However, it’s important to note that the boundaries of these routing keys don’t always align with expectations. For example, parts of County Meath fall under the D15 routing key, despite not being in Dublin at all.

What are routing keys used for?

Routing keys are used primarily by An Post for sorting and delivering mail based on post towns. While they are sometimes visible in public datasets—such as statistics published by the CSO—this is largely because they offer a level of detail more granular than counties.

However, routing keys were not designed for use in service planning or administrative boundaries. In fact, Eircode’s design deliberately avoided making the codes hierarchical or suitable for such purposes. Planning and analysis for things like schools, healthcare, and elections are instead based on standard administrative divisions such as Small Areas and Electoral Divisions, which provide consistent, defined geographic boundaries.

List of routing keys

In total, there are 139 Eircode routing keys for the Republic of Ireland.  Below is a table highlighting each one with the corresponding area: