When I try to install Craft CMS 3 by going to /admin the site redirects me to /index.php?p=admin/install where the Begin button shows. Clicking next send me to the screen to create an admin user.

When I enter all the information I see an ajax call going to http://domain.com/index.php?p=admin/actions/install/validate-account but that responds with 400 Error.

Any idea whats wrong? I have .htaccess file in place, so not sure why I see the index.php part in the url. Any help would be appreciated. Edit: in the error log file I see those three lines

[-][-][error][yii\i18n\PhpMessageSource::loadMessages] The message file for category 'yii' does not exist: /home/rrznjzkn/public_html/craft3/craft/app/vendor/yiisoft/yii2/messages/en-US/yii.php Fallback file does not exist as well: /home/rrznjzkn/public_html/craft3/craft/app/vendor/yiisoft/yii2/messages/en/yii.php

[-][-][warning][craft\app\web\ErrorHandler::handleException] 400 - Unable to verify your data submission.

[-][-][error][yii\web\HttpException:400] exception 'yii\web\BadRequestHttpException' with message 'Unable to verify your data submission.' in /home/rrznjzkn/public_html/craft3/craft/app/vendor/yiisoft/yii2/web/Controller.php:110
  • I wouldn't recommend using Craft 3 yet... it's still in "developer preview", it hasn't even reached the "beta" phase yet. You might want to stick with the current version of Craft 2 until some formal announcements are made about 3.
    – Lindsey D
    Commented Jun 28, 2016 at 16:30
  • @Lindsey D: I tend to agree with you on this and would vote to close it but I don't think it's an "official" stance of the community yet... Commented Jun 28, 2016 at 20:50
  • @RitterKnight: Yeah, that's fair. I didn't VTC... just giving the OP a warning about being in uncharted territory. :)
    – Lindsey D
    Commented Jun 28, 2016 at 20:55
  • OK, thank you. I will stick with Craft 2 for now.
    – svetlin
    Commented Jun 29, 2016 at 10:19
  • Same problem with craft 2.6
    – dazz
    Commented Nov 28, 2017 at 13:47

1 Answer 1


You're getting that error because CSRF validation is failing. Whether that's a bug in the Dev Preview of Craft 3 or something environmental on your end is hard to tell with the given information. I can't reproduce it locally, though.

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