PageSpeed Optimization Libraries (PSOL)
PSOL was Google's server-independent C++ optimization engine — the core inside mod_pagespeed that rewrote HTML, CSS, JavaScript, and images. Google archived it in 2020. The engine kept working, and it's still maintained. Here's how to run it today.
What PSOL was
A set of C++ classes that optimized web pages and the resources they load, independent of any one web server. The same core powered mod_pagespeed on Apache and ngx_pagespeed on nginx. It ran on Linux, and building it meant building mod_pagespeed first.
What happened to it
Google released its final open-source version in 2020 and archived the project. Development continued at We-Amp B.V., founded by a former mod_pagespeed maintainer. The optimization algorithms PSOL proved across billions of pages still ship today — patched for CVEs, built on modern toolchains, and supported.
Run the optimization engine today
PSOL is no longer a standalone build target. The same core now ships three ways. Pick the one that matches where your HTML lives.
In your web server — mod_pagespeed 1.1
A drop-in module for Apache, nginx, IIS, and Envoy. Your existing mod_pagespeed configuration keeps working.
Read the 1.1 docs →In front of any origin — ModPageSpeed 2.0
A separate worker process optimizes any HTTP origin and is driven by an HTTP API. Nothing to compile into your server.
Inside ASP.NET Core — WeAmp.PageSpeed
A NuGet package runs the native C/C++ core inside your .NET request pipeline via P/Invoke. No reverse proxy, no sidecar.
Install via NuGet →Looking for the old API docs?
The Doxygen class reference that lived at /psol/hierarchy.html is gone, and we don't publish PSOL as a standalone library to link against. If you came here
for programmatic access to the optimization engine, the 2.0 worker HTTP API is the maintained
equivalent — every endpoint the web console uses is open to your own scripts.