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Linker error · RAM

Fix ESP32 “region `dram0_0_seg' overflowed by … bytes”

Global and static variables don’t fit the ESP32’s static RAM. Shrink big global arrays, allocate large buffers at runtime with malloc/PSRAM, or move constants to flash.

ESP32ESP32-S3ESP32-C3ESP32-CAMUpdated 3 Nov 2026

Community draft — report a mistake

What you see

OutputOutput
ld.exe: CameraLogger.ino.elf section `.dram0.bss' will not fit in region `dram0_0_seg'
ld.exe: DRAM segment data does not fit.
ld.exe: DRAM segment data does not fit.
ld.exe: region `dram0_0_seg' overflowed by 97544 bytes
collect2.exe: error: ld returned 1 exit status
exit status 1

Compilation error: exit status 1

The linker places every global and static variable into a fixed region of RAM called dram0_0_seg. If they add up to more than that region, the build fails with the exact overflow in bytes — before anything is uploaded.

// Before: 200 KB static array -> overflow
// uint8_t frame[200000];

uint8_t* frame = nullptr;

void setup() {
  Serial.begin(115200);
  frame = (uint8_t*)(psramFound() ? ps_malloc(200000) : malloc(200000));
  if (!frame) Serial.println("Not enough RAM for frame buffer");
}

Quick fix — try in order

  1. 1

    Find the big global

    Look for global arrays like uint8_t frame[200000]; or char log[50000];. Statically allocated data on a classic ESP32 must fit in roughly 160–180 KB, shared with Wi-Fi and the core.

  2. 2

    Allocate large buffers at runtime

    uint8_t* frame = (uint8_t*)malloc(200000); in setup() uses the heap, which can use RAM regions that static data can’t. Check the pointer isn’t NULL.

  3. 3

    Use PSRAM if the board has it

    ESP32-CAM, WROVER and many S3 modules have 2–8 MB PSRAM. Enable it (Tools → PSRAM: Enabled) and use ps_malloc(size) for images and big tables.

  4. 4

    Put constant tables in flash

    Mark fonts, lookup tables and images const (e.g. const uint8_t logo[] = {…};). Const data stays in flash and doesn’t use DRAM.

  5. 5

    Read which section overflowed

    .dram0.bss = zero-initialised globals; .dram0.data = globals with initial values. The overflow number is how much to trim.

Why it happens

The ESP32 has 520 KB of RAM — why so little?

The 520 KB is split into instruction RAM, data RAM, cache and memory reserved by Wi-Fi/Bluetooth. Static (compile-time) data can only use part of the data RAM; the heap gets the rest.

Same code fits on an ESP32-S3

Different chips have different memory maps. The S3 and C3 have more contiguous data RAM than the original ESP32.

Variant: section `.iram0.text' will not fit in region `iram0_0_seg'

Too much code marked IRAM_ATTR. Only interrupt handlers and the functions they call need it.

Board-specific notes

ESP32-CAM: Camera frame buffers belong in PSRAM, set via config.fb_location = CAMERA_FB_IN_PSRAM — see PSRAM not found if it isn’t detected.

Related: Too much code rather than data: Sketch too big.

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