Here are two methods you can use to check OneDrive free space and available storage capacity.
OneDrive is a cloud-based storage from Microsoft that offers 5GB of space for free for every customer. Microsoft 365 (formerly Office 365) subscribers get 1TB with no additional cost as part of their plan, but those who need even more space can upgrade up to 2TB. Microsoft used to offer unlimited storage to Microsoft 365 subscribers, but the company ditched that option several years ago following some cases of unlimited storage abuse. Still, 2TB is more than enough for a vast majority of users.