On this page, you will find more information about the most common causes and most relevant solutions for the Minecraft error 'java.io.IOException: Server returned HTTP response code: 503'. Do you need help straight away? Visit our support page.
The Mojang Studios documentation indicates that error code 'java.io.IOException: Server returned HTTP response code: 503' is caused by the following problem: "The server cannot authenticate your account because minecraft.net is down.".
Do you think there is another cause for this error? Let others know in the comments.
Try again later when the Minecraft authentication servers have returned to normal.
Do you still have problems with this error? Try one of the quick fixes below or leave a comment.