As experienced WordPress administrators who've resolved this issue for countless sites, we know how frustrating the 'Upload: Failed to write file to disk' error can be. Follow our expert-tested steps to get back to seamless file uploads.
This error typically stems from incorrect folder permissions, a common culprit on WordPress sites. Every file and folder has permissions that dictate web server access.
Wrong permissions block the server from writing new files, preventing uploads from the admin dashboard.
When attempting uploads, you'll see messages like:
Connect to your site using an FTP client like the free FileZilla (interfaces may vary slightly with others).
Right-click the wp-content folder and select File permissions.
The dialog displays permissions for owner, group, and public. Enter 755 in the numeric value field.
Check 'Recurse into subdirectories', then select 'Apply to directories only'.
Click OK to set 755 permissions on wp-content and all subfolders, including uploads directories.
Next, repeat for files: Right-click wp-content, select permissions, enter 644, check 'Recurse into subdirectories', and choose 'Apply to files only'.
Click OK. This ensures proper 644 permissions for all files.
Return to your WordPress dashboard and test uploading a file.
If the error persists, contact your hosting provider to clear the server's temporary files directory. WordPress uses PHP's temp directory for initial uploads before moving to wp-content/uploads. A full or misconfigured temp dir blocks this process, and hosts can flush it since it's not FTP-accessible.
These steps, refined from years of troubleshooting WordPress sites, should resolve the issue. For more, see our guide on fixing common WordPress image problems.
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