Looking for logging into the Salesforce Developer Sandbox site and are not getting the correct working link for it? In such a case, you can use the links given here by searching your desired login page in the search box. If the page is present on our website then you will get all the links related to the Salesforce Developer Sandbox site. After that you can login as usual with your login credentials.
https://developer.salesforce.com/forums/%3Fid%3D906F00000008kVjIAI
https://login.salesforce.com/
https://developer.salesforce.com/signup
https://success.salesforce.com/answers%3Fid%3D90630000000h1A1AAI
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_intro_get_dev_account.htm
https://help.salesforce.com/apex/HTViewHelpDoc%3Fid%3Ddata_sandbox_create.htm%26language%3Den
https://help.salesforce.com/apex/HTViewHelpDoc%3Fid%3Dcreate_test_instance.htm%26language%3Den_us
https://help.salesforce.com/htviewsolution%3Fid%3D000175987
https://help.salesforce.com/apex/HTViewHelpDoc%3Fid%3Ddata_sandbox_implementation_tips.htm
https://help.salesforce.com/articleView%3Fid%3Doverview_edition.htm%26type%3D5
https://workbench.developerforce.com/
https://www.tutorialkart.com/salesforce/salesforce-sandbox-login-test-salesforce-com/
https://salesforce.stackexchange.com/questions/209567/how-do-i-grant-an-external-vendor-developer-development-access