Privacy by design: what it is and how to apply it
"Privacy by design" is one of those phrases you read everywhere and rarely understand. It is often treated as a document to attach to a project, a box to tick before going live. In reality it is not a piece of paperwork: it is the way software is conceived and built from the very first line, so that it protects people's data without anyone having to remember to do so afterwards. What the GDPR actually says The principle is written plainly in Article 25 of the GDPR, which speaks of "data protection by design and by default". These are two distinct things. Protection by design concerns the choices made while the system is being built. Protection by default concerns how the system behaves the moment it is switched on, before anyone touches a single setting. The law does not mandate a specific technology. It asks for an outcome: that data protection be built into the system, proportionate to the risks, and not bolted on afterwards as a patch. It is a difference of substance, not of form. A well-designed system does not have to chase compliance: it already has it inside. It is not a document, it is an architecture The most common mistake is to reduce privacy by design to a file. A report is written, filed, and the building goes on exactly as before. But a PDF protects no data. What protects data are the technical decisions: what information is collected, where it is stored, who can see it, how long it stays, what happens when it is no longer needed. These decisions are made at design time, and changing them later costs far more than getting them right at the start. The principles, turned into concrete choices Privacy by design becomes useful only when it stops being a slogan and turns into a series of choices. Translated into practice, the principles sound like this. Minimisation. You collect only the data genuinely needed to deliver the service. A field you do not collect does not need protecting, cannot be lost in a breach, does not need keeping. The safest piece of da