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I'm working with an Arduino Mega 2560 and am getting the following error at compile time:

avrdude: verification error, first mismatch in byte 0x0000 0x14! = 0x25 avrdude: verification error; content mismatch

I've already changed the COM port and also restarted an IDE.

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    This is not a compilation error but an error when verifying the programmed memory. – Eugene Sh. Sep 21 '17 at 18:48
  • Do you have the Board set correctly? Tools->Board. – Steve G Sep 21 '17 at 20:08
  • Do you have an old Mega2560 and have !!! somewhere in your code? – Majenko Sep 21 '17 at 21:13
  • First mismatch in byte 0x0000. Is that the first byte that goes wrong ? That means that not even a single byte passes the verification ? Perhaps the cause is one of these: 1) A cheap clone with a bad bootloader. 2) An old bootloader. 3) A bug, perhaps a bug with the size of the code or ram, for example the code at the border of 32k or 64k. 4) Maybe the voltage of the Arduino board is too low. Measure it. It must be above 4.5V. 5) Maybe a bad usb cable. 6) Wrong usb driver. 7) Board is too cheap and is missing decoupling capacitors. – Jot Sep 21 '17 at 21:18
  • I have seen this myself. It turned out that coms were a little distorted. If you have access to one, use an oscilloscope to view the waveforms of the 4 ISP pins. – sa_leinad Dec 18 '18 at 15:23
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I have made Jot's comment into an answer in the hope that it helps someone.


First mismatch in byte 0x0000. [This is] the first byte that goes wrong. That means that not even a single byte passes the verification.

Perhaps the cause is one of these:

  1. A cheap clone with a bad bootloader.
  2. An old bootloader.
  3. A bug, perhaps a bug with the size of the code or ram, for example the code at the border of 32k or 64k.
  4. Maybe the voltage of the Arduino board is too low. Measure it. It must be above 4.5V.
  5. Maybe a bad USB cable.
  6. Wrong USB driver.
  7. Board is too cheap and is missing decoupling capacitors.

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