Are drops in Google ranking common after switching to https?

Yes it is common. We get questions about it here all the time:

• Huge drop (50%) in traffic after HTTPS move
• Search traffic dropped with HTTPS implementation
• Organic Traffic down after HTTPS (SSL) move (2 months passed)
• Why my website is excluding from search results after migration to https?
• Which penalties are possible when switching from HTTP to HTTPS

We also have questions about whether Google will rank sites better with HTTPS:

• Will http to https rewrite rule affect SEO ranking?
• In terms of rankings how much 'MORE' does Google reward for HTTPS enabled websites

I recently moved my largest website to HTTPS (millions of monthly SEO visits). I did so without any problems with Google rankings. I did it in 3 stages:

1. Enable both HTTP and HTTPS with canonicals on HTTP (2 years, although this could just be a quick test)
2. Switch the canonicals to HTTPS (9 months)
3. Redirect HTTP to HTTPS

For full details see my answer to HTTP to HTTPS: Wait for new sitemap to be indexed?

It will take time for Google to merge the index listings for your old site with your new URLs. This kind of temporary drop is normal.

Keep an eye on the 301 redirects and wait for your listings to recover.

• Do you have a "rel=canonical" tag in your page that points to a HTTP url rather than a HTTPS?
• Do you have residual links inside your webpage that point to HTTP version of your webpages rather than the HTTPS version. (for instance, an <img src=http://)
• I would encourage you to check all the redirect headers and response. In the HTTP response, you should not see a HTTP either in the HTTP headers or the HTML.