Fix “data section exceeds available space in board” (Uno/Nano)

What you see

Sketch uses 1696 bytes (5%) of program storage space. Maximum is 32256 bytes.
Global variables use 2288 bytes (111%) of dynamic memory, leaving -240 bytes for local variables. Maximum is 2048 bytes.
Not enough memory; see https://support.arduino.cc/hc/en-us/articles/360013825179 for tips on reducing your footprint.
data section exceeds available space in board

Compilation error: data section exceeds available space in board

Sketch uses 1696 bytes (5%) of program storage space. Maximum is 32256 bytes.
Global variables use 2288 bytes (111%) of dynamic memory, leaving -240 bytes for local variables. Maximum is 2048 bytes.
Not enough memory; see https://support.arduino.cc/hc/en-us/articles/360013825179 for tips on reducing your footprint.
data section exceeds available space in board

Compilation error: data section exceeds available space in board

Quick fix — try in order

1. 1

   Wrap fixed text in F()

   Serial.println(F("Sensor not found")); and lcd.print(F("Tank level"));. Without F(), every string literal is copied into RAM at start-up.

   Tried it
2. 2

   Shrink arrays and buffers

   A byte log[1000] or int readings[500] eats half the Uno. Use byte instead of int where values fit 0–255, and keep only the samples you need.

   Tried it
3. 3

   Put constant tables in PROGMEM

   const uint8_t table[] PROGMEM = {…}; and read with pgm_read_byte(&table[i]).

   Tried it
4. 4

   Check library buffers

   Some libraries reserve big buffers: SD (~600 B), an SSD1306 128×64 (1 KB at runtime), WS2812 (3 B per LED). Two of them together rarely fit an Uno.

   Tried it
5. 5

   Change board if the project is simply bigger

   Mega 2560 has 8 KB RAM; ESP32 has over 300 KB. Often cheaper than hours of trimming.

   Tried it

Why it happens

Board-specific notes