Fixing \"419 Page Expired\" after deploying

A 419 error means the CSRF token did not match. The usual causes after a deploy:

- APP_URL does not match the address you open (http vs https, www vs no www).
- SESSION_DOMAIN is set to the wrong domain.
- The storage/framework/sessions folder is not writable (when SESSION_DRIVER=file).
- A cached config from another server — run php artisan optimize:clear then php artisan optimize.

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