Magento can't login to admin panel

Common cause: the login actually succeeds but Magento cannot persist the session (so you get bounced back to the login page with no error). This is especially common on local installs (Chrome/Chromium + localhost) or when cookie/base‑URL settings don’t match the site domain. @Member#949455’s question about “local or online” is the right first diagnostic. (magento.stackexchange.com)

Checklist (execute in order, backing up the DB and files first):

1. Quick checks: clear browser cookies or use a private window and confirm an adminhtml cookie appears after a login attempt.

2. Clear sessions and cache on the server (Magento 1.x): run

   rm -rf var/session/* var/cache/*

   and ensure var/, var/session/ and var/cache/ are writable by the webserver user. Too many session files or an unwritable session path will cause the redirect loop. (stackoverflow.com)

3. If that doesn’t help, remove cookie overrides in the DB (backup DB first). Example SQL to run in phpMyAdmin or mysql client:

   
   UPDATE core_config_data
   SET value = NULL
   WHERE path IN ('web/cookie/cookie_domain','web/cookie/cookie_path');

UPDATE core_config_data
SET value = 0
WHERE path = 'web/cookie/cookie_httponly';

Unset cookie domain on localhost or make it match your actual domain (use `.example.com` only when you require subdomain cookies). ([magento.stackexchange.com](https://magento.stackexchange.com/questions/160775/unable-to-login-to-admin-no-error-message-stuck-at-login-screen?utm_source=openai))

4) Confirm unsecure/secure base URLs (with or without `www`) are consistent and that `web/secure/use_in_adminhtml` is set appropriately if you use HTTPS. Incorrect base URL vs cookie domain causes the same symptom. ([magento.stackexchange.com](https://magento.stackexchange.com/questions/104659/magento-customer-login-and-admin-login-session-cookie-issue?utm_source=openai))

Notes and cautions: back up the DB before editing `core_config_data`; don’t run destructive shell commands from the wrong directory; check `php.ini` `session.save_path` and server time skew; if `app/etc/local.xml` forces a nonstandard `session_save` (files vs db) verify that target storage is writable. @SidRhyes’s suggestion to recheck signup is less likely to help here — focus on cookie/session, file perms, and base-URL settings.