How to add a comment in a Laravel .env file?

To add a comment in a Laravel .env file, you can use a # Hash.

For example,

# Test Settings
MAIL_MAILER=mailhog
MAIL_HOST=
MAIL_PORT=
MAIL_USERNAME=
MAIL_PASSWORD=
MAIL_ENCRYPTION=

# Live Settings
MAIL_MAILER=sendgrid
MAIL_HOST=
MAIL_PORT=
MAIL_USERNAME=
MAIL_PASSWORD=
MAIL_ENCRYPTION=