Apache Traffic Server vs Varnish Cache
Apache Traffic Server
trafficserver.apache.org
Varnish Cache
varnish.orgSide by side
| Figure | Apache Traffic Server | Varnish Cache |
|---|---|---|
| Price from | Free | Free |
| Free plan | Yes | Yes |
| Free trial | — | — |
| Open source | Yes | — |
| macOS | Yes | — |
| Linux | Yes | Yes |
| API | Yes | — |
| Self-hosted | Yes | Yes |
| Plans published | 1 | 1 |
| Spec score · Reverse Proxy Software | 9.0 (#2) | 7.3 (#21) |
| Spec score · Caching Software | 8.9 (#2) | 7.3 (#16) |
| Purpose | Apache Traffic Server is a fast, scalable, extensible HTTP/1.1 and HTTP/2 caching proxy server. | Varnish Cache is a reverse caching proxy that serves cached responses from memory and proxies other requests to origin servers. |
| Security | Security options include client access controls, client authentication, SSL termination, and access control via SSL. | The security guide describes four control levels: command-line arguments, the CLI interface, VCL programs, and HTTP requests. |
| Support | Users can seek help through the Users Mailing List or ASF Slack, and code questions through the developers discussion list. | The project points users to Discord, Stack Overflow, and LinkedIn, and says commercial support is available through Varnish Software. |
Plans
In their own words
Apache Traffic Server
Apache Traffic Server is a free, open-source caching proxy server for HTTP/1.1 and HTTP/2. It stores frequently requested pages, images, and web service calls so they can be reused, with the stated aims of improving response time and reducing server load and bandwidth needs. It can also add keep-alive behavior, filter or anonymize requests, and balance traffic through a proxy layer. Deployment patterns include web proxy cache, reverse proxy, and cache hierarchy. As a layer 7 HTTP load balancer, it can choose next-hop servers using request attributes, weighted round robin, or URL consistent hashing. Plug-in APIs let teams add behavior such as changing headers, handling ESI requests, or implementing cache algorithms. Security options include client access controls and authentication, SSL termination, and SSL-based access control. It is self-hosted, with Linux and macOS listed as platforms. The project identifies enterprises, internet service providers, backbone providers, and large intranets as its intended audience. The listed stable release is 10.2.0; 9.2.15 is listed as the long-term support release.
Varnish Cache
Varnish Cache is a reverse caching proxy for Linux and self-hosted deployments. It serves cached responses from memory and sends other requests to origin servers. Its caching policy is defined in Varnish Configuration Language (VCL), which compiles to native code. Cached objects follow standard HTTP cache headers and leave the cache when they expire. Varnish supports TLS termination within the process and TLS connections to dynamic origin backends. It includes varnishlog for structured logging and varnishstat for metrics, and offers official container images and a Kubernetes Helm chart. Installation guidance covers Debian, Ubuntu, Red Hat Enterprise Linux, and compatible distributions. Varnish modules add functions callable from VCL. Its security guide describes controls at the command-line, CLI, VCL, and HTTP request levels. The free plan costs nothing. One limit to account for: Varnish avoids caching data when it cannot determine that doing so is safe, and applications may need configuration changes to reach a high cache hit rate.