How to check how much flash space is available on MikroTik RouterOS

Using WebFig (Web UI)

Click on System on the left, then click on Resources. You can see the free space on the flash as Free HDD Space:

Using the command line

Enter the following command:

/system resource print

and look for the free-hdd-space line - for example:

[admin@CoreSwitch01] > /system resource print
                   uptime: 4d19h26m41s
                  version: 7.4.1 (stable)
               build-time: Aug/04/2022 11:48:11
         factory-software: 6.44.6
              free-memory: 408.7MiB
             total-memory: 512.0MiB
                      cpu: ARM
                cpu-count: 2
                 cpu-load: 26%
           free-hdd-space: 44.0KiB
          total-hdd-space: 15.9MiB
  write-sect-since-reboot: 35547
         write-sect-total: 520339
               bad-blocks: 0%
        architecture-name: arm
               board-name: CRS309-1G-8S+
                 platform: MikroTik