What this problem is
Media uploads fail or WordPress cannot write thumbnails because wp-content/uploads permissions are incorrect.
Why it happens
- Migration changed file ownership
- Permissions were hardened incorrectly
- Hosting user mismatch
Prerequisites
- FTP/File Manager access
Diagnosis
Check upload errors in Media. Verify permissions and ownership on wp-content/uploads and current year/month folders.
Detailed steps
Step 1) Set recommended permissions
- Folders: 755
- Files: 644
Step 2) Verify ownership
The web server user must be able to write. On shared hosting, this is typically your account user.
Step 3) Retest uploads and thumbnail generation
Upload a small image and confirm WordPress creates thumbnails.
Expected results
- Uploads succeed and thumbnails generate correctly
What to do if it fails
- Ask hosting support to correct ownership recursively on uploads
Best practices
- Avoid using 777 permissions; use the minimum required