As the central registry for all domains ending in .de, we live by our motto, ‘.de for a responsible internet.’ In our blog, we would like to introduce our solution for validating postal address data: OpenPAQ.
What is OpenPAQ?
OpenPAQ stands for Open Postal Address Quality – an open source tool developed by DENIC in cooperation with the CENTR community. It was specifically designed to evaluate addresses as they are actually used by people in practice – including abbreviations, additional information, multilingualism, typos and non-standard formats. Unlike conventional approaches, which compare addresses with an official address list, OpenPAQ recognises which addresses actually exist – and does not just check whether they comply with a standardised format. OpenPAQ stands out in particular because it evaluates individual address components (street, city, postcode, country) separately and can identify the incorrect part of an address.
European cooperation for higher quality
During the development phase, the high number of international registrations of .de domains posed a particular challenge for our data science team, especially with regard to the processing of foreign addresses.
For this reason, we initiated a task force with seven different European registries and incorporated country-specific findings on the use of postal addresses into the development process. For more information on the collaboration, see CENTR News.
Thanks to the excellent cooperation, we were able to significantly increase the performance of OpenPAQ. Using an internal benchmark with realistic test data consisting of 90 correct and 40 incorrect addresses per country, we were able to demonstrate that accuracy has increased by more than 10 percent on average. For addresses from FR, GB, PL, DK, IT, and the US an accuracy of more than 75 percent was achieved. Addresses from DE, NL, CH, and AT even achieved a top performance of more than 90 percent accuracy. We presented these promising results in May 2025 at the CENTR Jamboree, an event organised by the CENTR community, where we celebrated our success together.
Why is address validation so important?
The validation of postal addresses will play a central role in the registration process as part of risk assessment in the future. Incorrectly classified addresses – regardless of whether they are actually incorrect or mistakenly identified as ‘invalid’ – increase the likelihood that our DENIC members will need to verify the domain holder. This causes increased effort for both our members and our domain owners. The better OpenPAQ works, the fewer unnecessary verifications are required and additional effort is minimised. At the same time, registrations with fake address data are prevented, which significantly strengthens the trustworthiness of .de domains.
Get involved and actively shape OpenPAQ
OpenPAQ is open source and everyone is welcome to further develop the project and help optimise it. Everyone is welcome to contribute – whether through feedback, improvements to the source code or suggestions for validation scenarios. Just visit https://openpaq.de/ and contribute.
Because every contribution helps to strengthen trust in .de!
