Here's How to Find IP Address of All Devices on Network

Setting up a new Raspberry Pi 4 or Pi 5 without a graphic interface (desktop mode or headless mode) from another computer is tricky. Especially, when you don't know the IP address of all the devices that connect to your network. For remote access, you'll mostly use the SSH (Secure Shell) network protocol to set it up securely. But, if you can't seem to open the raspberrypi.local (default hostname of Raspberry Pi) via SSH from your Windows or Mac, then you'll need to find the local IP address of the Raspberry Pi unit.
Of course, you could run the command arp -a in the Command Prompt (Windows) or Terminal (macOS, Linux), but it may not show the hostnames of all the devices. Luckily, tools like Angry IP Scanner can discover the IP address and hostnames of all devices on the network. Download and install the Angry IP Scanner app for your Windows PC or Mac. After that, launch the app and define the IP range you want the app to scan to get more accurate results. Typically, you'll find a Class C IP range (192.168.0.0 - 192.168.255.255) that your router assigns to all the local devices on your network.
Hit the Start button and let it scan the IP address of the devices on the network. The Angry IP Scanner will scan the predefined range and present the results.
You'll need to look at the Hostname column of the app, which shows all the devices on your network, including your Raspberry Pi unit. You'll notice the green, blue, and red dots in front of IP addresses. A green dot means an active IP address and connected device has open ports that responds to Angry IP scanner's ping requests. A blue dot means an active IP address, but the connected device doesn't respond to Angry IP scanner's pings. Meanwhile, a red dot means an inactive IP address and no device connected.
Note that you won't always find the host names in the app. That happens when the device's local name (hostname) is different than the one linked with the IP address (global name). In the case of your Raspberry Pi, if you didn't input a hostname while creating an SD card, the default raspberrypi.local will appear.