crt-sh
crt.sh | Certificate Search
- Dead simple; enter the domain and get a list of all issued certificates on one page
- Doesn't include all information, but clicking on the ID provides the full certificate
- Can also be helpful in quickly getting an idea for site development (first time a cert was requested, etc.)
- Using Advanced search, you can also look for domains that contain any string
- For example, companies making look-alike domains for twitter.
