Let's Encrypt production ACME API logs errors after an upstream network event

Category: Outage
Status: developing
Sources: Let's Encrypt status, discussion
Summary: Let's Encrypt's status page recorded an incident on its production ACME API (acme-v02.api.letsencrypt.org) starting 2026-06-18 16:04 UTC. An upstream network event disrupted traffic between two of its datacenters, and some clients received 400 and 500 responses while most requests still succeeded. As of the 2026-06-19 04:45 UTC update the API was operating normally but with reduced redundancy, with Let's Encrypt still working with its upstream ISP to resolve the root cause. The matching HN thread surfaced on 2026-06-19 as renewal errors.
Why it matters: Let's Encrypt issues certificates for a large share of the public web, so renewal failures during the window risk expired certificates for clients without retry headroom.
Follow-up: Watch for full redundancy restoration and any Let's Encrypt post-incident note.