🧩 How hidden unicode characters can break your system

Introduction While working on a feature that sends notifications to phone numbers, I recently faced one of the trickiest bugs I’ve encountered. Everything looked correct the phone number was valid, the logs seemed fine, and yet the system kept rejecting the request. After digging deeper, the culprit turned out to be something almost invisible: hidden Unicode character inside the phone number. In this article, I’ll explain: What Unicode characters are What hidden Unicode characters are How they can silently break your systems The real bug I faced How I solved it What Are Unicode Characters? Computers represent text using numeric codes. Early systems used ASCII, which only supported about 128 characters By using 7 bits to represent each character. Mainly English letters, digits, and basic symbols. To support all languages, symbols and emojis, the industry adopted the Unicode standard. Unicode assigns a unique code point to every character. Examples: Character Unicode Code Point A U+0041