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Riemann vs Prometheus Alertmanager: catalog facts
Riemann	Prometheus Alertmanager
Free Free to download and run.	Free Free and open source as part of the Prometheus project.
Linux, Self-hosted	Self-hosted
Low-latency stream processing of monitoring events Flexible rules written as Clojure code	Groups hundreds of related alerts into one notification Silencing and inhibition to cut alert noise
Configuration requires learning Clojure syntax Keeps transient state rather than long-term storage	Configured through files rather than a full graphical interface Designed around Prometheus and its alerting rules
Downloadable app, Self-hosted	Downloadable app, Self-hosted
Closed source	Open source
License not stated	License not stated
No account needed	No account needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked October 1, 2026	Official website Full listing and sources Checked September 23, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.