what are the drawbacks to changed my website Http to Https?
 

what are the drawbacks to changed my website Http to Https?

Here's a list of benefits and drawbacks for you. Although there are drawbacks, Google prefers https and gives it a boost in SEO rankings. https://moz.com/blog/seo-tips-https-ssl

It affect more because the site from HTTP is converted to https and it is considered as a new one so we should start creating new backlinks from first.

there are lot of other things as well which are not listed here. SEO is most important.

If you have a social sharing widget on your blog post pages, all of your Facebook "likes" for that page will be gone.
You had several blog posts that had several hundred Facebook likes and when you switched to https. They will go.

a small boost in rankings (possibly larger in the future)
a more secure site for your users

It is slower (encrypting and decrypting takes time).

It can scare users when things go (even slightly) wrong. Mixed content warnings, expired certificates, invalid certificates will cause many browsers to present scary warnings to the user.

It is more complicated. Your server needs to redirect non-https traffic, you need to do configuration and install certificates, make sure they are valid and up to date.

It is costly, you need to pay for ssl certificates (or use a self-signed one, but that is not generally a realistic option).

It affects the backlinks.

I’ve seen sites recover from this mistake when switching, but it seems to only happen several months later, when Google figures out what happened and corrects the mistake on their end.