Why Does My ESP32 Keep Restarting or Crashing After Upload?

#Introduction

Uploaded your sketch successfully, but the ESP32 just keeps restarting again and again? Or maybe it runs for a few seconds and then crashes? Don't worry — you're not alone. In this post, we’ll break down the most common reasons why your ESP32 keeps resetting or crashing after uploading code, and how you can fix it quickly.

#What Does "Restarting" Look Like?

You'll often see messages like these in the Serial Monitor:

ets Jun 8 2016 00:22:57
rst:0xc (SW_CPU_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
...

Or sometimes you see:

Guru Meditation Error: Core 1 panic'ed (LoadProhibited). Exception was unhandled.

These are clear signs that something is going wrong after code upload.

#Common Reasons Why Your ESP32 is Restarting or Crashing

#1. Power Supply Issue

If you're powering your ESP32 from a weak USB port or a bad cable, it may not be getting enough current — especially during Wi-Fi or Bluetooth startup.

#Fix:

• Use a high-quality USB cable and connect to a proper USB 3.0 port.
• Try using a 5V 1A power supply (phone charger + USB cable).

#2. Watchdog Timer Resets

ESP32 has watchdog timers that reset the chip if code gets stuck in a loop or takes too long in one task.

#Fix:

• Make sure you use delay() or yield() in long loops to prevent watchdog resets.
• Avoid infinite while loops without breaks.

#3. Faulty Peripherals or Sensors

If something connected to the GPIO pins is shorted or drawing too much power, the ESP32 might crash or enter a reboot loop.

#Fix:

• Disconnect everything from GPIO pins and test with only USB connected.
• Reconnect peripherals one by one to find the culprit.

#4. Code Consumes Too Much RAM

Memory overflows can lead to crashes, especially if you’re using large arrays, images, or web server libraries.

#Fix:

• Use the ESP.getFreeHeap() function to monitor RAM usage.
• Optimize code: use String carefully, minimize global variables.

#5. GPIO Conflicts During Boot

Certain pins on the ESP32 must be in specific states at boot time. Using them incorrectly can cause boot loops.

#Fix: Avoid using these pins during startup:

• GPIO 0, 2, 15 – used for boot mode selection
• GPIO 6–11 – connected to flash memory internally

#6. Exception or Panic Errors

Guru Meditation Errors or panic dumps usually mean a memory or code execution problem.

#Fix:

• Recheck your code logic
• Use Serial.print() debugging to find the crashing line
• Simplify your code to isolate the problem

#Quick Checklist to Fix Restarting Issues

Check

What to Do

Power Supply

Use good USB cable / external 5V

Peripherals

Disconnect sensors & modules

Code

Avoid infinite loops, delays, large data

GPIO Pins

Don’t use 0, 2, 15 wrongly

Serial Monitor

Watch for crash messages

Flash Settings

Re-upload with correct board settings

#Bonus Tip: Use esp_reset_reason() in Code

Want to know why your ESP32 reset? Use this:

#include "esp_system.h"

void setup() { Serial.begin(115200); delay(1000); Serial.println("Reset reason: "); Serial.println(esp_reset_reason()); }

It will show messages like POWERON_RESET, SW_CPU_RESET, or DEEPSLEEP_RESET — helping you diagnose better.

#Conclusion

Crashes and restart loops may look scary, but most of the time the fix is simple: clean power, clean code, and correct pin usage. If your ESP32 is crashing right after upload, don’t panic — use the tips above to track down the cause, one step at a time.