My mum couldn't use WhatsApp because her font size is too large

My mum recently bought a new iPhone. She's very excited about it, mostly because it is a green colour.

I knew she had received it when I got the following message on iMessage:

I asked what exactly she meant when she said that WhatsApp didn't work. It turned out that she wasn't able to progress past this screen:

The UI is very messed up - and she couldn't press the next button because it was being overlapped by other elements. This meant that she couldn't enter her phone number to verify her account, and so could never use WhatsApp.

Now, I know that my mum has the font size on her phone set quite large. And having done web development, I am well aware that most products are never tested in anything but the most typical circumstances. It seemed quite possible that this UI just couldn't handle a different font size.

I suggested she reduce her font size temporarily and see if that fixed the issue. As soon as she did this, it worked perfectly and she was able to get into WhatsApp.

Conclusion

• It's disappointing that WhatsApp doesn't handle this case. There are a lot of people who change the font size on their phones for various good reasons. How many of them are going to be able to figure out that this is what's preventing them from using WhatsApp?
• Developers will never test their work on anything but what they consider to be the most typical setups.
• I thought Meta were supposed to be a highly optimised user acquisition engine? What happened?