SSL/TLS Certificate Lookup
Check a domain's SSL/TLS certificate — who issued it, when it expires, and whether the chain is trusted
open-book.ru
SSL/TLS Certificate
SSL/TLS Certificate for open-book.ru
Valid- Issued by (CA)
- Let's Encrypt
- Subject
- open-book.ru
- Valid from
- Aug 6, 2026
- Valid until
- Nov 4, 2026 (43 days remaining)
- Public key
- RSA 2048-bit
- Serial
- 0682AEB3274DE84075953AD9EAAB29D63AB3
- SHA-256 fingerprint
- 21:88:D7:4D:66:D9:78:2F:44:96:D4:08:C5:F0:49:AC:EF:62:20:4F:88:24:F0:71:CD:B1:8B:C4:0F:A2:46:07
- Chain
- YR1 → Root YR → ISRG Root X1
Certificate Authority Authorization (CAA)
No CAA policy is published for this domain — any certificate authority may issue for it.
This certificate has been served since Sep 21, 2026.
Never get surprised by open-book.ru's certificate expiring
This is today's certificate. Turn on monitoring and we'll watch open-book.ru continuously, notifying you the moment anything moves across all three signals:
Uptime
We visit the site from multiple regions worldwide and email you within minutes if it goes down, with a per-region breakdown so a real outage stands out from a regional blip.
DNS changes
We watch NS, MX, CAA, DNSSEC, CNAME and A/AAAA records, and identify the host, network, and ASN behind them, so a real migration or hijack stands out from routine noise.
TLS certificate
We warn you 30, 14, 7, and 1 days before it expires, and flag it if the issuing authority changes or the certificate is unexpectedly replaced.
Free for your first domain: uptime, DNS, and certificate together. No credit card.