Decide which file formats the network actually needs and how much storage each site should use. Check the hosting account's total disk allowance and backup impact. Do not enable executable or unsafe formats merely because a user wants to upload them through the Media Library.

1. Sign in as a Super Admin and open Network Admin > Settings > Network Settings.
2. Review the Upload Settings area, including site upload space and maximum individual file size where shown.
3. Review the allowed file extensions using the format expected by the field, normally space-separated extension names without dots.
4. Save the approved policy and inspect any site-specific storage overrides.
5. Test a permitted file and a deliberately disallowed file using a normal subsite user account.

PHP upload and request limits, available disk space, server rules and security plugins can impose a lower effective limit. An image may also require more processing memory than its compressed file size suggests. Identify the exact rejection message and the responsible layer before increasing multiple settings.

No. The network list filters types that WordPress recognises and permits. Adding an extension alone does not necessarily register a safe MIME type or bypass core validation. Use a maintained, security-reviewed solution for a legitimate new format, and avoid blanket upload bypasses.

Check that users see a helpful limit and know how to optimise oversized media. Prefer appropriately sized images and a suitable video-delivery service when large videos would exhaust account storage. Deleting a file from the server manually can leave broken Media Library references, so clean up through an understood content workflow.

Test uploads, generated image sizes and public display on representative subsites. Record the reason for each exception and review it periodically. A per-site quota does not create additional hosting capacity; the network still shares the account's resources and backup responsibilities.

• Adding a new site to an existing WordPress Multisite network
• Planning backups for a WordPress Multisite network
• Archiving a Multisite subsite instead of deleting it
• Extracting one Multisite subsite into an independent installation

• WordPress: Settings
• WordPress: Check Upload Mimes
• WordPress documentation