I like having serial communication for debugging and testing purposes but after a while it takes away too much speed from the sketch.

Is it possible to have the Arduino ignore serial.print and serial.println throughout my code, without turning it into a comment or placing every serial printing inside for example "if(debug == true)" statements?

Thanks in advance.

3 Answers 3


If you insist on top performance, the best thing would be to use a macro for that:

#define Sprintln(a) (Serial.println(a))

Then instead of

Serial.println(F("Hello world!"));


Sprintln(F("Hello world!"));

etc. To deactivate the Serial printing, define the macro empty:

#define Sprintln(a) 

This will have the preprocessor remove all debugging code defined with Sprintln from your code.

(Of course, there's a huge number of variations on this theme.)

  • 1
    You can also wrap all exiting prints in #ifdef ENABLE_PRINT and #endif and then define or comment out #define ENABLE_PRINT at the top of ur file
    – benathon
    Commented Apr 5, 2015 at 12:20
  • 1
    You can even set a debug level and define macro's for debugL1();, debugL2(); etc, so you can choose how many details you want to "log". The macro's will though make it unable to change runtime, but at the advantage of not having runtime overhead.
    – aaa
    Commented Oct 4, 2016 at 20:04

You could, for example, use the preprocessor to change all Serial in your code.

// disable Serial output
#define Serial SomeOtherwiseUnusedName
static class {
    void begin(...) {}
    void print(...) {}
    void println(...) {}
} Serial;

Yet another solution is to implement a dummy Serial device. That would be a class that as HardwareSerial inherits from Stream and implements the necessary virtual member functions with dummy functions.

class NullSerial : public Stream {
  virtual size_t write(uint8_t) { return (1); }
  virtual int available() { return (0); }
  virtual int read() { return (0); }
  virtual int peek() { return (0); }
  virtual void flush() {}
  void begin(unsigned long, uint8_t) {}
  void end() {}

NullSerial Serial;

As Serial is not defined as a weak symbol the application would need to use a Steam variable for output. And bind this to the HardwareSerial or the NullSerial.

#if defined(DEBUG)
Stream& trace = Serial;
NullSerial noSerial;
Stream& trace = noSerial;


This is not complete as all the HardwareSerial member functions (that the sketch uses) are needed but gives the general idea how to use OOP to solve the problem.


  • This worked well for me (great for debugging in PlatformIO!). Instead of declaring NullSerial Serial (which conflicts with the HardwareSerial declaration by the same name), I gave it a unique name (NullSerial nullSerial) and then overrode the original everywhere with #define Serial nullSerial. Lovely thing about this method is that my existing code does not change. Commented Aug 19, 2023 at 13:45

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