user67963: I'm using this tutorial to connect my ESP8266-01 WiFi Module to Arduino UNO with Arduino IDE v. 1.8.13.

It works and the module can connect to my WiFi.
However, when I try to upload my code, it says:
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x30
What could be the problem, since when I remove the reset pin it uploads the code, but now the WiFi goes down.

user4143: Your problem is that there are two ways of wiring your ESP-01 module to the Arduino:

Wired so the PC has access to it and the Arduino is effectively disabled, and
Wired so the Arduino has access to it

You are wired in configuration 1 at the moment whereby the Arduino is effectively turned off and the USB connection goes direct to the ESP-01. When you try and upload code to the Arduino it's the ESP-01 that the computer is talking to, not the Arduino.
You need to wire it in configuration 2. In this configuration the TX/RX pins of the ESP-01 connect to any two pins of the Arduino except pins 0 and 1, and the RESET pin is not connected to anything. Then you can't talk to the ESP-01 through the serial monitor - instead you have to write code for the Arduino that uses SoftwareSerial to communicate for you.
There are many many tutorials online about communicating between the Arduino and the ESP-01.

67963: <p>I'm using <a href="http://www.teomaragakis.com/hardware/electronics/how-to-connect-an-esp8266-to-an-arduino-uno/" rel="nofollow noreferrer">this tutorial</a> to connect my ESP8266-01 WiFi Module to Arduino UNO with Arduino IDE v. 1.8.13.</p>
<p><a href="https://i.stack.imgur.com/QJYqb.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/QJYqb.png" alt="Tutorial snippet" /></a></p>
<p>It works and the module can connect to my WiFi.
However, when I try to upload my code, it says:</p>
<p><code>avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x30</code></p>
<p>What could be the problem, since when I remove the reset pin it uploads the code, but now the WiFi goes down.</p>
 4143: <p>Your problem is that there are two ways of wiring your ESP-01 module to the Arduino:</p>
<ol>
<li>Wired so the PC has access to it and the Arduino is effectively disabled, and</li>
<li>Wired so the Arduino has access to it</li>
</ol>
<p>You are wired in configuration 1 at the moment whereby the Arduino is effectively turned off and the USB connection goes direct to the ESP-01. When you try and upload code to the Arduino it's the ESP-01 that the computer is talking to, not the Arduino.</p>
<p>You need to wire it in configuration 2. In this configuration the TX/RX pins of the ESP-01 connect to any two pins of the Arduino except pins 0 and 1, and the RESET pin is not connected to anything. Then you can't talk to the ESP-01 through the serial monitor - instead you have to write code for the Arduino that uses SoftwareSerial to communicate for you.</p>
<p>There are many many tutorials online about communicating between the Arduino and the ESP-01.</p>
