Open-Source Observability · prometheus

alertmanager

Prometheus Alertmanager is a Go-based alert routing and management system that deduplicates, groups, and routes alerts from Prometheus and other sources to notification channels like email, PagerDuty, OpsGenie, and Slack. It handles alert silencing, inhibition rules, and webhook integrations.

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Source: GitHub — github.com/prometheus/alertmanager

8.5k

GitHub stars

2.4k

Forks

Primary language

Apache-2.0

License (OSI-approved)

Key facts

Objective fields from the source. Values we can't verify are shown as “Unknown” rather than guessed.

Field	Value
Repository	prometheus/alertmanager
Owner	prometheus
Primary language	Go
License	Apache-2.0 — OSI-approved
Stars	8.5k
Forks	2.4k
Open issues	427
Latest release	v0.33.1 (2026-07-04)
Last updated	2026-07-06
Source	https://github.com/prometheus/alertmanager

What alertmanager is

Alertmanager receives alerts via HTTP API, applies configurable routing trees with label-based matching, deduplicates and groups alerts by configurable dimensions, and forwards to receiver integrations. Provides OpenAPI v2 specification, REST API with v2 endpoint prefix, and amtool CLI for programmatic interaction. Built in Go with YAML configuration.

Quickstart

Get the alertmanager source

Clone the repository and explore it locally.

terminalbash

1git clone https://github.com/prometheus/alertmanager.git2cd alertmanager3# follow the project's README for install & configuration

Need it deployed, integrated, or customized instead? DEV.co ships production installs.

Best use cases

Prometheus ecosystem integration

Purpose-built receiver for Prometheus Server alerts; tightly integrated with Prometheus monitoring stack without external dependencies.

Multi-channel alert routing at scale

Hierarchical routing rules, label-based matching, and grouping strategies reduce alert fatigue and ensure appropriate teams receive relevant alerts.

Alert lifecycle management

Native support for silencing, inhibition rules, and repeat intervals provides fine-grained control over alert suppression and escalation without modifying alert sources.

Implementation considerations

Requires Prometheus-compatible alert source or webhook integration for ingestion; Alertmanager does not generate alerts independently.
YAML configuration is declarative and version-controllable but changes require service restart or API reload; plan configuration deployment workflow.
Receiver credentials (API keys, SMTP passwords) must be stored securely outside YAML (e.g., environment variables, secrets manager) to avoid exposure.
High-availability deployment requires state file sharing (file system or external store) for alert deduplication and silencing state across instances.
Alert grouping and repeat intervals significantly impact notification volume; requires tuning based on alert velocity and organization SLAs.

When to avoid it — and what to weigh

Not a metrics collection system — Alertmanager only handles alert routing and management. Requires Prometheus or compatible alert source; does not collect or store metrics itself.
Minimal out-of-box visualization — Web UI is functional for status/silencing but not a primary dashboard platform. Organizations requiring rich alert dashboards should layer additional tooling.
Custom receiver logic complexity — While webhook receiver allows extensibility, implementing complex custom logic requires external webhook handlers; no built-in templating engine for all integrations.
Stateless design trade-offs — Alertmanager is largely stateless; advanced multi-tenant or complex historical audit trails may require external persistence or wrapper layers.

License & commercial use

Apache License 2.0 (Apache-2.0) — permissive OSI-approved license permitting commercial use, modification, and distribution with liability disclaimer and requirement to retain license notices.

Apache-2.0 explicitly permits commercial use, distribution, and modification without royalties or license fees. Organizations may deploy, embed, or offer Alertmanager-based services. Recommend legal review if modifying and reselling; upstream contribution of improvements benefits ecosystem.

DEV.co evaluation signals

Editorial assessment — not user reviews. Directional, with an explicit confidence level.

Signal	Assessment
Maintenance	Active
Documentation	Strong
License clarity	Clear
Deployment complexity	Low
DEV.co fit	Strong
Assessment confidence	High

Security considerations

Configuration must not hardcode credentials; use environment variables or secrets management for receiver API keys and SMTP passwords. TLS support available for webhook receivers and integrations; verify TLS enforcement in deployment. Alert data in transit and at rest depends on transport layer and receiver configuration. No known critical CVEs in recent releases; check upstream security advisories before deploying.

Alternatives to consider

Grafana OnCall

Cloud-native alert management with richer UI, incident workflow, and built-in on-call scheduling; requires external SaaS or self-hosted deployment; tighter Grafana integration than Prometheus ecosystem.

Opsgenie (Atlassian)

SaaS alert management and routing platform with native mobile app, on-call management, and escalation policies; integrates with Alertmanager as receiver but adds cost and cloud dependency.

VictorOps / Splunk On-Call

Incident response platform with alert aggregation, rich UI, and on-call management; similar receiver-based integration model but offers more advanced workflows at higher cost.

Software development agency

Build on alertmanager with DEV.co software developers

Deploy Alertmanager to centralize alert routing, reduce fatigue, and streamline incident response across your Prometheus infrastructure.

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Related open-source tools

Surfaced by semantic similarity across the DEV.co open-source index.

prometheus-operator promgen WatchAlert

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alertmanager FAQ

Does Alertmanager collect or store metrics?

No. Alertmanager only handles alert routing, deduplication, and management. Metrics collection and evaluation are handled by Prometheus Server or compatible alert sources. Alertmanager can store alert state and silencing rules but not time-series metrics.

How is state managed in a highly available Alertmanager deployment?

Alertmanager stores state (silences, inhibitions) in a local file. For HA, multiple instances require access to a shared state file via NFS, object storage, or other shared file systems. Alertmanager does not natively cluster; state synchronization must be configured externally.

Can Alertmanager integrate with systems other than Prometheus?

Yes, via the webhook receiver or direct API v2 calls. Any system that can POST JSON alerts to the Alertmanager API can integrate. Detailed API documentation is available in the OpenAPI v2 specification.

What is the difference between inhibition rules and silencing?

Silencing manually suppresses specific alerts for a defined time window via API or UI. Inhibition rules automatically suppress alerts based on conditions (e.g., mute warnings if critical alert firing); defined in YAML configuration and evaluated on each alert.

Software developers & web developers for hire

DEV.co is a software development agency delivering custom software development services to companies building on open source. Our software developers and web developers design, integrate, and ship production systems — spanning web development, APIs, AI, data, and cloud. If alertmanager is part of your open-source observability roadmap, our team can implement, customize, migrate, and maintain it.

Integrate Alertmanager into your monitoring stack

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