Is crt.sh down?

Live availability check, refreshed every 60 seconds.

crt.sh is up — responded in 3403ms

HTTP 200 from crt.sh JSON endpoint · checked just now

Looking for a faster alternative anyway?

CT Radar indexes the same public Certificate Transparency logs that crt.sh does — Google Argon, Cloudflare Nimbus, DigiCert Wyvern, Sectigo Elephant, and more. Sub-second search, no rate-limit surprises.

Try: ···

Why does crt.sh go down so often?

crt.sh runs as a single-instance PostgreSQL database hosted by Sectigo as a free public good. There is no CDN, no read replica, and no multi-region failover. A single expensive query — or a brief spike in traffic — can take the whole service down or push it into long timeouts.

The maintainer Rob Stradling does heroic work keeping it running, but the architecture has not changed materially in years. If your recon pipeline cannot tolerate crt.sh being down for an hour, you need a backup data source.

How CT Radar stays up

Custom Rust LSM-tree backend — no PostgreSQL bottleneck on hot reads.
Memory-mapped FST indexes serve prefix queries from page cache, not disk seeks.
Independent ingestion — the crawler keeps syncing CT logs even when the query layer is under load.
Backed by Cloudflare on the edge — global presence, DDoS-protected.

Note: CT Radar and crt.sh consume the same upstream CT logs. They show the same certificates. CT Radar is faster and has an API — that is the difference.