What is a nonce?
The term 'nonce' is a portmanteau of 'number used only once': every single transaction you send from your MetaMask wallet has one, and the number (starting with 0 for the first transaction you send) increases in increments of 1.
Each transaction's nonce is an identifier that ensures your transactions are processed by the network in the correct order, preventing 'double spend' scenarios.
In MetaMask, adjusting the nonce can be useful if you need to speed up or cancel pending transactions.
How do I customize the nonce when sending a transaction?
Customizing the nonce isn't possible unless you enable it. To do so, head to settings by clicking the three vertical dots in the top right of your wallet, then go to Settings > Advanced:
Start to send a transaction from your wallet. Enter the recipient address and the value, and click 'Next'. Before you confirm the transaction, you'll see a breakdown of the gas fees and other details that looks like this:
Click the 'Custom nonce' field to enter the number you need, and, when you're ready to submit the transaction, 'Confirm'.
Customizing the nonce isn't possible unless you enable it. To do so, head to settings by tapping the gear icon in the tab bar, and then going to the 'Advanced':
Start to send a transaction, and input the recipient's address and the value you want to send. Now tap 'Next', and you'll be taken to a screen that looks like this:
When you tap the highlighted 'Edit' text next to the nonce field, you'll be able to customize it using the plus and minus buttons:
Press 'Save' to confirm your choice.