Converting a string to lower case

Converting a string to lower case

How to:

Arduino’s String object has a handy toLowerCase() method. Call it on your string, and just like that, it’s in lowercase.

void setup() {
  String message = "Hello, World!";
  Serial.println(message);  // Outputs: hello, world!

void loop() {
  // Nothing to do here.

Fire up your Serial Monitor, and you’ll see “hello, world!” printed out.

Deep Dive

Historically, dealing with text often involved accounting for upper and lower case. Data entry, search, and sort operations typically ignore case to reduce user error and increase robustness. In other languages, like C, you’d iterate over each character and convert them individually using standard library functions. In Arduino land, String objects wrap this functionality for ease of use.

Alternatives? Sure. You might use toLowerCase() for a char array, but you’ll have to walk through each character and convert it with tolower() from <ctype.h>. If you’re concerned about memory and performance, consider using character arrays over String objects and take control with your custom lowercasing logic.

See Also