Why the Login Page Sends You Right Back to Itself
Every WordPress login attempt sets an authentication cookie, and every subsequent wp-admin page checks that cookie before showing the dashboard. A redirect loop means that check keeps failing silently — WordPress accepts the password, tries to send you to wp-admin, the cookie check fails, and it bounces you back to login, over and over. The fix is finding which part of that cookie-and-URL chain is broken.
Step 1: Clear Cookies and Try a Private Window
Before touching any files, clear your browser's cookies for the site, or simply try logging in from a private/incognito window. A stale, corrupted, or conflicting authentication cookie is one of the most common causes, and this rules it out — or fixes it — in under a minute.
Step 2: Check for a Site Address / WordPress Address Mismatch
If cookies aren't the issue, the next most common cause is a mismatch between the WordPress Address (URL) and Site Address (URL) values — for example, one set to http:// and the other to https://, or a leftover www. inconsistency after a domain change. Since this mismatch is exactly what's blocking wp-admin access, you can't fix it through the dashboard — instead, add these two lines to wp-config.php via FTP (with your actual site URL):
define( 'WP_HOME', 'https://yoursite.com' );
define( 'WP_SITEURL', 'https://yoursite.com' );
This overrides the database values directly, which resolves the loop immediately if a mismatch was the cause. Once you're able to log in again, go to Settings > General and correct both fields properly, then you can remove these lines from wp-config.php.
Step 3: Rule Out a Plugin Conflict
Security plugins and caching plugins are the most frequent culprits here, since both commonly interact with cookies and sessions. Rename the /wp-content/plugins folder via FTP to deactivate every plugin at once, then try logging in again. If it works, rename the folder back and reactivate plugins one at a time until the loop returns — that identifies the plugin responsible.
Step 4: Check for a Corrupted .htaccess File
Rename .htaccess to .htaccess-old via FTP and attempt to log in again. If that resolves the loop, the original file had a bad rewrite rule. After logging in, go to Settings > Permalinks and click Save Changes to regenerate a clean .htaccess automatically.
