Fixing pre-flight URL errors
What the pre-flight check tests and how to fix CORS, hotlink and format failures.
Before you can publish, we load your URL in the browser to make sure other people will actually see it. The check verifies the link resolves, returns a real image, and isn't blocked by your host.
- Not an image — the link points at a web page, not a file. Right-click your image and choose 'Copy image address'.
- Blocked or forbidden (403) — your host blocks hotlinking. Allow this domain in your hotlink protection settings, or disable hotlink protection for that folder.
- CORS error — your server needs to permit cross-origin loading. Add an Access-Control-Allow-Origin header for images.
- Not found (404) — the file was moved or renamed. Re-check the path.
- Very large file — technically fine, but slow for viewers. Aim for under a few megabytes.
Cloudflare, Nginx and cPanel all have hotlink protection switched on in some presets — that's the most common cause of a failing check.