Regardless of being or not logged in to Facebook, when I access a profile username URL like https://www.facebook.com/someusername (note this is not the username in question) I am redirected to Facebook homepage.  I have read What are the guidelines around creating a custom username for my Page or profile? and The username I want isn't available help articles but I am unable to figure out in which case is an error displayed and in which one redirection happens.  How do I find out in what cases Facebook performs redirection instead of showing the more common The link you followed may be broken, or the page may have been removed message?  In response to comments, here is the HTTP dialogue between my browser and facebook server (not exactly a network capture but what Chrome tells me in the inspect console; a tcpdump wouldn't have worked anyway because of encryption):Remote Address:173.252.120.6:443Request URL:https://www.facebook.com/mydesiredusernameRequest Method:GETStatus Code:302 forced.302Request Headers:host:www.facebook.com:method:GET:path:/mydesiredusername:scheme:https:version:HTTP/1.1accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8accept-encoding:gzip,deflateaccept-language:en-US,en;q=0.8,ro;q=0.6user-agent:Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2138.3 Safari/537.36  Response Headerscache-control:private, no-cache, no-store, must-revalidatecontent-length:0content-security-policy:default-src *;script-src https://*.facebook.com http://*.facebook.com https://*.fbcdn.net http://*.fbcdn.net *.facebook.net *.google-analytics.com *.virtualearth.net *.google.com 127.0.0.1:* *.spotilocal.com:* 'unsafe-inline' 'unsafe-eval' https://*.akamaihd.net http://*.akamaihd.net *.atlassolutions.com chrome-extension://lifbcibllhkdhoafpjfnlhfpfgnpldfl;style-src * 'unsafe-inline';connect-src https://*.facebook.com http://*.facebook.com https://*.fbcdn.net http://*.fbcdn.net *.facebook.net *.spotilocal.com:* https://*.akamaihd.net wss://*.facebook.com:* ws://*.facebook.com:* http://*.akamaihd.net https://fb.scanandcleanlocal.com:* *.atlassolutions.com http://attachment.fbsbx.com https://attachment.fbsbx.com;content-type:text/html; charset=utf-8date:Fri, 29 Aug 2014 15:18:48 GMTexpires:Sat, 01 Jan 2000 00:00:00 GMTlocation:https://www.facebook.com/p3p:CP=Facebook does not have a P3P policy. Learn why here: http://fb.me/p3ppragma:no-cacheset-cookie:next_path=%2Fmydesiredusername; path=/; domain=.facebook.com; httponlyset-cookie:next=https%3A%2F%2Fwww.facebook.com%2Fmydesiredusername; path=/; domain=.facebook.com; httponlyset-cookie:datr=gL40VKc9de7X2JkAkAa8pC6d; expires=Sun, 28-Aug-2016 15:18:48 GMT; Max-Age=63072000; path=/; domain=.facebook.com; httponlystatus:302 forced.302strict-transport-security:max-age=15552000version:HTTP/1.1x-content-type-options:nosniffx-fb-debug:eG4PPd7AXspQtvCrF0QpDa8O83xqPwXmp71aLaELCSsd9EmWUpUTaR5giSBxSMnD8EcXi3dJS54PsnsVshL0mg==x-frame-options:DENYx-xss-protection:0And this is the different response for another username that DOES exist:  Remote Address:173.252.120.6:443Request URL:https://www.facebook.com/zuckRequest Method:GETStatus Code:200 OK  Request Headers:host:www.facebook.com:method:GET:path:/zuck:scheme:https:version:HTTP/1.1accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8accept-encoding:gzip,deflateaccept-language:en-US,en;q=0.8,ro;q=0.6cookie:datr=2JkAVKcAa8pC6gL407Xd9dek; next=https%3A%2F%2Fwww.facebook.com%2Fcostinel; next_path=%2Fcostinel; reg_fb_ref=https%3A%2F%2Fwww.facebook.com%2F; reg_fb_gate=https%3A%2F%2Fwww.facebook.com%2Fuser-agent:Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2138.3 Safari/537.36  Response Headerscache-control:private, no-cache, no-store, must-revalidatecontent-encoding:gzipcontent-security-policy:default-src *;script-src https://*.facebook.com http://*.facebook.com https://*.fbcdn.net http://*.fbcdn.net *.facebook.net *.google-analytics.com *.virtualearth.net *.google.com 127.0.0.1:* *.spotilocal.com:* 'unsafe-inline' 'unsafe-eval' https://*.akamaihd.net http://*.akamaihd.net *.atlassolutions.com chrome-extension://lifbcibllhkdhoafpjfnlhfpfgnpldfl;style-src * 'unsafe-inline';connect-src https://*.facebook.com http://*.facebook.com https://*.fbcdn.net http://*.fbcdn.net *.facebook.net *.spotilocal.com:* https://*.akamaihd.net wss://*.facebook.com:* ws://*.facebook.com:* http://*.akamaihd.net https://fb.scanandcleanlocal.com:* *.atlassolutions.com http://attachment.fbsbx.com https://attachment.fbsbx.com;content-type:text/html; charset=utf-8date:Fri, 29 Aug 2014 15:42:43 GMTexpires:Sat, 01 Jan 2000 00:00:00 GMTp3p:CP=Facebook does not have a P3P policy. Learn why here: http://fb.me/p3ppragma:no-cacheset-cookie:reg_fb_ref=https%3A%2F%2Fwww.facebook.com%2Fzuck; path=/; domain=.facebook.comset-cookie:reg_ext_ref=deleted; expires=Thu, 01-Jan-1970 00:00:01 GMT; Max-Age=0; path=/; domain=.facebook.comstatus:200 OKstrict-transport-security:max-age=15552000version:HTTP/1.1x-content-type-options:nosniffx-fb-debug:0wJCS7YL4wH7ZWIloMFBlzzylt5wW4V3fjaOJJ4vsfCzuiljp3ggQQnYwyAkMHujWHkkSstCdV8CCAo+i6Cf+Q==x-frame-options:DENYx-xss-protection:0And finally this is the response when the username does not exist:  Remote Address:173.252.120.6:443Request URL:https://www.facebook.com/zuckdoesnotexistRequest Method:GETStatus Code:404 Not Found  Request Headers:host:www.facebook.com:method:GET:path:/zuckdoesnotexist:scheme:https:version:HTTP/1.1accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8accept-encoding:gzip,deflateaccept-language:en-US,en;q=0.8,ro;q=0.6cookie:datr=2JkAVKcAa8pC6gL407Xd9dek; next=https%3A%2F%2Fwww.facebook.com%2Fcostinel; next_path=%2Fcostinel; reg_fb_gate=https%3A%2F%2Fwww.facebook.com%2F; reg_fb_ref=https%3A%2F%2Fwww.facebook.com%2Fzuckuser-agent:Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2138.3 Safari/537.36  Response Headerscache-control:private, no-cache, no-store, must-revalidatecontent-encoding:gzipcontent-security-policy:default-src *;script-src https://*.facebook.com http://*.facebook.com https://*.fbcdn.net http://*.fbcdn.net *.facebook.net *.google-analytics.com *.virtualearth.net *.google.com 127.0.0.1:* *.spotilocal.com:* 'unsafe-inline' 'unsafe-eval' https://*.akamaihd.net http://*.akamaihd.net *.atlassolutions.com chrome-extension://lifbcibllhkdhoafpjfnlhfpfgnpldfl;style-src * 'unsafe-inline';connect-src https://*.facebook.com http://*.facebook.com https://*.fbcdn.net http://*.fbcdn.net *.facebook.net *.spotilocal.com:* https://*.akamaihd.net wss://*.facebook.com:* ws://*.facebook.com:* http://*.akamaihd.net https://fb.scanandcleanlocal.com:* *.atlassolutions.com http://attachment.fbsbx.com https://attachment.fbsbx.com;content-type:text/html; charset=utf-8date:Fri, 29 Aug 2014 15:46:35 GMTexpires:Sat, 01 Jan 2000 00:00:00 GMTp3p:CP=Facebook does not have a P3P policy. Learn why here: http://fb.me/p3ppragma:no-cacheset-cookie:reg_fb_ref=https%3A%2F%2Fwww.facebook.com%2Fzuckdoesnotexist; path=/; domain=.facebook.comset-cookie:reg_ext_ref=deleted; expires=Thu, 01-Jan-1970 00:00:01 GMT; Max-Age=0; path=/; domain=.facebook.comstatus:404 Not Foundstrict-transport-security:max-age=15552000version:HTTP/1.1x-content-type-options:nosniffx-fb-debug:zJHNyJNzOhh58U9V8uJ0xF1sL9e/BTNMao+DN361Mv5IBZ+T36Y1a7uhZxbDyvzrhNrC2yMnKfMQj6q49Cg6HA==x-frame-options:DENYx-xss-protection:0  Observe the different 302, 200 and 404 HTTP statuses response for each case. Why is it issuing 302 in my case?  PLEASE NOTE that I am not interested in the technical reasons for issuing a 302 code (I can find that in the RFC), but rather in what is their policy for issuing a 302 redirect to their front page when requesting a particular profile name that seems to not exist but be unavaiable when choosing it at https://www.facebook.com/username, at the same time!
Why is Facebook redirecting to homepage when accessing a particular profile name?
facebook;facebook username