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Grafana Loki vs Prometheus

Grafana Loki logo

Grafana Loki

Software

Log Aggregation for Grafana Stack

From
Free
Rated
-
Full reviewWebsite
Prometheus logo

Prometheus

Software

Open source monitoring and alerting toolkit for cloud native environments

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Grafana Loki grafana Cloud Logs Pro plan includes only 30-day retention; retention beyond 30 days requires Enterprise plan with minimum $25,000 annual commitment; Prometheus not suitable for per-request billing as collected data lacks 100% accuracy
  • They diverge on capability: Grafana Loki covers Log aggregation, Prometheus covers Multi-dimensional Data Model.

Where they differ

Only the attributes on which Grafana Loki and Prometheus actually diverge.

Attributes where Grafana Loki and Prometheus differ
AttributeGrafana LokiPrometheus
Pricing modelfreemiumopen-source
PlatformsSelf-hosted (open source), Managed (Grafana Cloud Logs), Enterprise (self-managed with support)Linux, macOS, Windows
Founded20142015

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated), category (Unknown).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Grafana Loki

  • Log aggregation
  • Label-based indexing
  • LogQL language
  • Cost-effective
  • API
  • Webhooks
  • REST
  • Web support

Only in Prometheus

  • Multi-dimensional Data Model
  • PromQL Query Language
  • Pull-based Collection
  • Service Discovery
  • Alerting Rules
  • Federation
  • Local Storage
  • Grafana

What people use each for

The jobs each tool is most often brought in to do.

Grafana Loki

  • Cost-sensitive organisations deploying Kubernetes and Prometheus ecosystemsnot Prometheus
  • Teams needing index-free log aggregation for high-volume environmentsnot Prometheus

Prometheus

  • Cloud-native monitoring and alertingnot Grafana Loki
  • Time-series metrics collectionnot Grafana Loki
  • Infrastructure monitoringnot Grafana Loki

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Grafana Loki

  • Grafana Cloud Logs Pro plan includes only 30-day retention; retention beyond 30 days requires Enterprise plan with minimum $25,000 annual commitment
  • Open-source version requires self-hosting all infrastructure including storage and scaling

Prometheus

  • Not suitable for per-request billing as collected data lacks 100% accuracy
  • Hard limit on scrape body size; large responses cause scrape failure
  • Per-scrape sample limit enforced; exceeding limit marks targets as failed
  • Not designed for long-term durable storage; optimised for metrics collection

Pricing, plan by plan

Grafana Loki

Free

No published plan breakdown. See the Grafana Loki review.

Prometheus

Free

No published plan breakdown. See the Prometheus review.

Which should you pick?

Choose Grafana Loki if

  • You need log aggregation.
  • You want to start without paying.
  • You work on Self-hosted (open source), Managed (Grafana Cloud Logs), Enterprise (self-managed with support).
  • You also want label-based indexing.
Grafana Loki review

Choose Prometheus if

  • You need multi-dimensional data model.
  • You want to start without paying.
  • You work on Linux, macOS, Windows.
  • You also want promql query language.
Prometheus review

Questions people ask

Is Grafana Loki or Prometheus better?
Neither clearly leads. Grafana Loki starts at Free and Prometheus at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Grafana Loki or Prometheus?
Grafana Loki starts at Free and Prometheus at Free.
Does Grafana Loki or Prometheus run on more platforms?
Grafana Loki runs on Self-hosted (open source), Managed (Grafana Cloud Logs), Enterprise (self-managed with support). Prometheus runs on Linux, macOS, Windows.
Can I use Grafana Loki for free?
Both have a free tier, so you can try either at no cost before committing.
What is Grafana Loki best used for?
Grafana Loki is most often used for cost-sensitive organisations deploying kubernetes and prometheus ecosystems, teams needing index-free log aggregation for high-volume environments. Of those, cost-sensitive organisations deploying kubernetes and prometheus ecosystems and teams needing index-free log aggregation for high-volume environments are not what Prometheus is typically brought in for.
What can Grafana Loki do that Prometheus cannot?
Grafana Loki covers Log aggregation, Label-based indexing, LogQL language, Cost-effective. Prometheus covers Multi-dimensional Data Model, PromQL Query Language, Pull-based Collection, Service Discovery.
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