User registration on two sites in same multisite

You could use a plugin such as
Join My Multisite – https://wordpress.org/plugins/join-my-multisite/

The plugin allows you to set if a user is a member of site1 and visits site2, automatically add site2 to the user’s sites. So you avoid them making another account.

Related Posts:

  1. How can I un-reserve a pending username registration?
  2. wordpress multisite, how to keep user on subdomain throughout registration process?
  3. Allowing periods in usernames
  4. Remove Site Name from register form – Multisite
  5. Prevent user creating new users with specific roles
  6. Get first_name and last_name on user_register hook
  7. Can’t add user to blog on registration (Multisite)
  8. Is there a wordpress function to cleanly delete an entry in the signups table?
  9. WordPress 3.2(Multisite) – How to add custom user meta fields to signup form?
  10. How to add multiple existing users to a multisite site?
  11. WPMU – new users are automatically subscribed to the main blog – how to prevent that?
  12. User registration on sub site
  13. Disable domain redirect
  14. Displaying a message upon user registration
  15. What sites are you registered to when joining a multisite?
  16. Add a user to a specific blog when they register?
  17. Auto creation of multisite blog on user registration
  18. Multisite – user email activation links broken
  19. Add menu items/actions for multisite users who are registered on the network but do not have a role or capability in any sites
  20. Four columns in the wp_users table
  21. WP MU Register User across all blogs
  22. Is the Multi site functionality a viable option for Country and Language targeting?
  23. Using the standard WordPress “New User” interface on a multisite
  24. How can you override the is_multisite check in wp-login.php for individual login/registration?
  25. How to change a user role after registering in multisite?
  26. How to fix that new users show up again in subsite of a Multisite?
  27. User registration is currently not allowed
  28. Multisite ‘Welcome User Email’ SITE_NAME returns ‘network’ name, not the name of the blog
  29. User registration on wordpress multisite
  30. Easily adding multiple existing users to a multisite site
  31. Automatic registration on main site upon user registration on Multisite
  32. Register a user only to the root blog – WP Multisite
  33. Activate User account for Sub Site broken
  34. Possible to have duplicate usernames on different two multisites
  35. How to allow mixed case characters in multisite site name?
  36. Modify new user email notification in network admin screen wp multisite
  37. Users getting linked unwanted to main mu in WordPress multisite (WPMU)
  38. Can’t activate a user on multisite install
  39. WordPress Multisite Network Subdomain
  40. Multisite: How to bypass wpmu_signup_user_notification and add my own notification logic?
  41. Allow users to register on multisite through WooCommerce using the same email address
  42. A different role for each site in a multisite
  43. Activation of new Registered site fails on multisite
  44. User registration problem on multisites web
  45. Multisite “Skip Confirmation Email” Log Out Problem
  46. Multisite – User creation for second site from first site?
  47. How to Create WPMu New User?
  48. Possible to set new user’s site time zone at user creation using Gravity Forms?
  49. multisite registration: check existing subdomains while typing
  50. Registration Page
  51. Using a number for limiting registering or banning on multisite
  52. How to use same email for multiple users? [duplicate]
  53. Programmatically create blogs with dummy content on a WPMU site
  54. How to individually set WP_DEBUG on a sub-directory multisite?
  55. Create multiple subdomains for multi-site from a database
  56. multisite htaccess 301 redirects
  57. using 1 form shortcode (si or cf7) for all multisite sites [closed]
  58. How to manage multiple domain with different languages on each domain with single wordpress installation?
  59. Redirect loop (only for multisite network admin)
  60. Deleting a user in multisite
  61. Recover from failed multisite conversion
  62. Cookie nonce is invalid – Multisite
  63. Multisite Network Localisation
  64. Can set_transient() be used in multi-site?
  65. What would you recommend for hosting 10+ individual wordpress websites?
  66. Redirect only posts to New Domain
  67. add_rewrite_rule on multisite doesn’t work
  68. web.config breaks the themes for sub-directory multisite
  69. Different use for WordPress Multisite
  70. Multisite User Sync Question about blog authorship
  71. WP-CLI cron on multisite using WP-Toolkit “succeded”, but callback not executed
  72. WordPress multisite suddenly malfunctioning
  73. Cannot use pre_set_site_transient_update_themes from within a theme in multisite
  74. Login problems on multisite installation with different domains
  75. FeedWordPress duplicated posts problem
  76. wp_get_attachment_image_src returns incorrect URL on multisite
  77. Locking one blog of many in a multi user/blog WordPress installation
  78. How do I disable XML-RPC in WordPress Multisite?
  79. Multisite – One Site with multiple URLs
  80. How to modify wp_config file for set up subdirectory?
  81. Activation Account Email
  82. How to automatically translate plugin using translate.wordpress.org
  83. May I do multiple micro-sites with different themes in a single wordpress without subdirectory nor subdomain separation?
  84. Multisite htaccess file causing segfault (Segmentation fault 11)
  85. Multisite Smtp Server
  86. Images uploaded after adding multisite do not get loaded in any domain of the multisite network
  87. When hooking wp-cron to system
  88. WordPress network, add extra directory to subsite urls
  89. Update Same Contents on every Page
  90. WooCommerce API Returns 401
  91. Define default settings for new sites on multisite network with mu-plugin
  92. Multisite + wp_mail – Route Via Site Conditionally
  93. MU domain mapping without using a plugin
  94. Multisite authorization error 401
  95. How create a multisite setup with “phantom” accounts and passwords?
  96. is there a if multisite have posts function?
  97. Multisite – mix sites that use subdomains with sites that use paths
  98. Pick your brain on wp-config.php if statement for multisite
  99. WordPress Multisite restict user access
  100. Change a subsite Admin role of a WordPress Multisite after 24 hours registering