How to remove (.html ) prefix from Contao url
Example : Currentl Url => http://example.com/startseite.html required url : http://example.com/startseite
You need to add the following to your config/config.yml
(app/config/config.yml
prior to Contao 4.9).
contao:
url_suffix: ''
After that, you need to clear and warmup the application cache, as with any configuration changes.