Can a Worker return 503 if the origin is not reachable? (fetch error handling)

@user6251 No, the error 502 means: BAD GATEWAY 503 meaning SERVICE TEMPORARILY UNAVAILABLE and 1016 meaning Origin DNS error If your orgin web server is down, then it will return error 520 or any error between 520 and 524, for troubleshooting 5xx errors visit https://support.cloudflare.com/hc/en-us/articles/115003011431-Troubleshooting-Cloudflare-5XX-errors#502504error