Quite often I see websites have postal code field input field even when the website or its input form has nothing to do with postal services. Here is one example (After entering email it will expand the form with additional information).
OK, I get the country field and city, that can be used for statistics, but why do they need postal code? I already entered the city, postal code will give information in which district I live, what is it for? They are not sending anything or even have plans to send anything in the future, this is useless. And this is not the only example, I see this quite often.
Fortunately, most of the time this is not required field, but in my opinion this is completely unnecessary both from functional point of view and from UX perspective.
Is there some reason behind it? Can postal code information about users can be used in any useful way at all? Or is it just bad design decision?

  • 1
    Whenever I see overly invasive forms I always imagine that the marketing department got involved. Nov 23, 2015 at 18:36
  • You get asked for your passport ID in nearly every Thai free-wifi zone. Why? Not sure other than to collect more data on you and to try and protect misuse (lol).
    – insidesin
    Jul 30, 2017 at 5:42

2 Answers 2


If you're in Canada:

A postal code can be used to verify a user has correctly entered their city and province and/or municipal address.

The "forward sorting area" portion of the postal code (first 3 characters) is used in a TON of statistical data and research in Canada. You can get household income, population data, etc. etc.

Are either of those things useful enough to piss off your user? Depends on what you're doing with it.

A good UX rule of thumb when collecting ANY data is to have a very clear explanation (not just the typical legal terms and conditions) about what you're DOING with that data.

  • In addition in Canada at least, retailers sometimes use this data to see where it makes sense to deliver flyers/catalogs to... Besides that, paired with a good search tool a postal code (6chars in Canada) can narrow down an address to which side of what street I live on much easier than typing in my full address)
    – scunliffe
    Nov 24, 2015 at 11:26

Where you live it may not be important. but for example like over here in Singapore postal code used a lot. e.g. taxi drivers prefer asking for your postal code as they can key it into their GPS and just follow directions without having to thing much. in my opinion this really depends on country. some countries use it more than others.

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