Varnish Cache

aid: varnish
name: Varnish Cache
description: Varnish Cache is a high-performance HTTP accelerator and reverse proxy designed for content-heavy dynamic websites
  and APIs. It sits in front of web servers and caches HTTP responses to serve repeated requests without hitting the backend,
  dramatically reducing load and latency. Varnish is configured via VCL (Varnish Configuration Language), a domain-specific
  language for request/response policy, and managed through a CLI interface (varnishadm) and a set of command-line tools for
  logging, statistics, and monitoring.
type: Index
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
tags:
- Caching
- Caching Proxy
- Content Delivery
- HTTP Accelerator
- Open Source
- Proxy
- Reverse Proxy
url: https://raw.githubusercontent.com/api-evangelist/varnish/refs/heads/main/apis.yml
created: '2026-03-27'
modified: '2026-05-03'
specificationVersion: '0.19'
apis:
- aid: varnish:varnish-cache
  name: Varnish Cache CLI API
  description: The Varnish Cache CLI management interface provides programmatic control over a running Varnish instance. It
    is accessible via varnishadm or TCP socket and supports configuration management (VCL load/use/discard), backend health
    control, cache ban/invalidation, parameter tuning, and process management. Commands can return JSON output with the -j
    flag.
  humanURL: https://varnish-cache.org/docs/trunk/reference/varnish-cli.html
  tags:
  - Cache Management
  - Caching
  - CLI
  - Configuration
  - Reverse Proxy
  properties:
  - type: Documentation
    url: https://varnish-cache.org/docs/trunk/reference/varnish-cli.html
  - type: GettingStarted
    url: https://varnish-cache.org/docs/trunk/users-guide/run_cli.html
  - type: APIReference
    url: https://varnish-cache.org/docs/trunk/reference/varnishadm.html
- aid: varnish:varnish-logging
  name: Varnish Logging Tools
  description: Varnish ships with a suite of log-analysis tools that read from the Varnish Shared Log (VSL). Tools include
    varnishlog (raw log streaming), varnishncsa (NCSA/Apache log format), varnishstat (live counters), varnishtop (real-time
    activity display), and varnishhist (response time histogram).
  humanURL: https://varnish-cache.org/docs/trunk/reference/
  tags:
  - Logging
  - Monitoring
  - Observability
  - Statistics
  properties:
  - type: Documentation
    url: https://varnish-cache.org/docs/trunk/reference/varnishlog.html
  - type: APIReference
    url: https://varnish-cache.org/docs/trunk/reference/varnishstat.html
- aid: varnish:varnish-vmods
  name: Varnish Modules (VMODs)
  description: VMODs are extensions written for Varnish Cache that extend VCL capabilities. Bundled modules include blob (binary
    data handling), cookie (HTTP cookie parsing), directors (load balancing strategies), h2 (HTTP/2 control), proxy (PROXY
    protocol support), purge (cache purging), std (standard utility functions), and unix (Unix socket support). Additional
    community VMODs are available for headers, digest, auth, and more.
  humanURL: https://varnish-cache.org/docs/trunk/reference/vmod.html
  tags:
  - Extensions
  - Modules
  - Plugins
  - VMODs
  properties:
  - type: Documentation
    url: https://varnish-cache.org/docs/trunk/reference/vmod.html
  - type: GitHubRepository
    url: https://github.com/varnishcache/varnish-cache
common:
- type: DomainSecurity
  url: security/varnish-domain-security.yml
- type: LinkedIn
  url: https://www.linkedin.com/company/varnish-software
- type: Website
  url: https://varnish-cache.org/
- type: Documentation
  url: https://varnish-cache.org/docs/
- type: GitHubOrganization
  url: https://github.com/varnishcache
- type: GitHubRepository
  url: https://github.com/varnishcache/varnish-cache
- type: ReleaseNotes
  url: https://varnish-cache.org/docs/trunk/whatsNew/
- type: Blog
  url: https://info.varnish-software.com/blog
- type: Forums
  url: https://discourse.varnish-cache.org/
- type: StackOverflow
  url: https://stackoverflow.com/questions/tagged/varnish
- type: Features
  data:
  - name: HTTP Caching
    description: Caches HTTP responses to reduce backend load and improve response times for repeated requests.
  - name: VCL Configuration Language
    description: Domain-specific language for defining request/response handling policies with full programmability.
  - name: CLI Management Interface
    description: TCP-based management interface for runtime configuration, VCL deployment, and cache control.
  - name: Backend Health Probes
    description: Configurable health checks for backends with automatic failover to healthy backends.
  - name: Cache Invalidation (Bans)
    description: Flexible cache invalidation via ban expressions matching any request/response attribute.
  - name: JSON Output
    description: CLI commands support -j flag for structured JSON output, enabling programmatic management.
  - name: VMOD Extension System
    description: Loadable modules (VMODs) extend VCL with cookie parsing, load balancing, digest, auth, and more.
  - name: HTTP/2 Support
    description: Native HTTP/2 support via the h2 VMOD for modern protocol acceleration.
  - name: Shared Memory Log (VSL)
    description: High-speed shared memory logging with rich request/response attributes for analysis tools.
  - name: Multi-threaded Architecture
    description: Worker thread pool for high-throughput concurrent request handling with configurable threading.
- type: UseCases
  data:
  - name: API Gateway Caching
    description: Cache REST API responses at the edge to reduce database and application server load.
  - name: CDN Origin Shield
    description: Act as origin shield between CDN edge nodes and web/application servers.
  - name: Static Asset Acceleration
    description: Cache and serve static assets (images, JS, CSS) with long TTLs.
  - name: A/B Testing
    description: Use VCL to route traffic fractions to different backends for controlled experiments.
  - name: DDoS Mitigation
    description: Absorb traffic spikes and rate-limit abusive clients via VCL policies.
  - name: Authentication Offloading
    description: Offload token validation and session checks to VCL logic at the cache layer.
  - name: Request Routing
    description: Route requests to different backend pools based on URL patterns, headers, or cookies.
- type: Integrations
  data:
  - name: Nginx
    description: Common deployment pairing with Nginx as backend web server behind Varnish.
  - name: Apache HTTP Server
    description: Classic deployment with Apache as origin server behind Varnish Cache.
  - name: Kubernetes
    description: Deployable as a sidecar or DaemonSet in Kubernetes clusters for service-level caching.
  - name: Prometheus
    description: Varnish statistics exportable via varnish_exporter for Prometheus scraping.
  - name: Grafana
    description: Community dashboards available for Varnish Cache statistics via Prometheus/Grafana.
  - name: Drupal
    description: Deep integration with Drupal Cache Tags for efficient purging of cached pages.
  - name: WordPress
    description: VCL configurations and plugins available for WordPress caching integration.
  - name: Fastly
    description: Fastly CDN is built on Varnish Cache; Fastly VCL is a fork of Varnish VCL.
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com