The HTTP 503 status code means the server can’t handle your request at this moment.
This status code is usually seen when the server is overloaded, under maintenance, or restarting.
Websites might also use this status code to block automated scraping. In such instances, it’s advisable to change the
User-Agent header to a string that resembles a browser and throttle requests. Also, check the robots.txt directives to make sure you’re abiding by them.
503 Service Unavailable is a proper code to return when a website is under maintenance. It signals to search engines that the downtime is temporary. Note that continuous 4xx or 5xx errors, including 503, might hurt search engine rankings and even result in the website/webpage being deindexed after some time.
Generally speaking, it’s better to keep maintenance windows short: a few minutes or hours is fine; several days isn’t. If you have a fixed date by which the maintenance will be completed, you might want to include a
Retry-After: Tue, 19 Jan 2038 03:14:07 GMT