When I enter save html through ckeditor I miss tag from the html content. Is there any ckeditor configuration I have to do to allow html tags such as inside html content? Thanks.
You have to use the allowedContent property when instantiating ckeditor to allow specific tags, or allowedContent: true to allow everything
https://docs.ckeditor.com/ckeditor4/latest/api/CKEDITOR_config.html#cfg-allowedContent
Either using config.js, or in-page configuration for the specified textarea:
https://docs.ckeditor.com/ckeditor4/latest/guide/dev_configuration.html
In my case (I am using a Symfony ckeditor bundle) I also can set it via bundle configuration inside config.yml.