Technical insights on web performance, automatic optimization, and the engineering behind mod_pagespeed 2.1 — the module and the optimizer worker.
How mod_pagespeed 2.1 shares one memory-mapped cache between nginx and the worker, serving large cache hits zero-copy with kernel sendfile and small ones with a single copy, while staying correct under concurrent writes.
Read post →The mod_pagespeed lineage and the ModPageSpeed 2.0 engine converge into one open-source product: the module you know, plus a separate optimizer worker. Apache-2.0, drop-in for 1.14/1.15 configs.
Read post →Head-to-head cache benchmark: Cyclone (memory-mapped, in-process RAM tier) vs. the classic file-per-entry cache, across concurrency, realistic traffic, latency tails, and eviction, on fast and realistic storage.
Read post →The agentic web creates four origin problems: identity, economics, what to serve, provenance. Where to solve them, and why on your own servers.
Read post →mod_pagespeed 2.1 ships an experimental, off-by-default RSL-CAP gate for nginx: validate Authorization: License capability tokens and refuse unauthorized AI-crawler access at your origin. Preview, not GA.
Read post →mod_pagespeed detects C2PA / Content Credentials manifests and preserves image provenance instead of stripping it when optimizing — on by default in both parts.
Read post →The mod_pagespeed 2.1 optimizer worker serves a clean markdown variant on Accept: text/markdown and synthesizes an /llms.txt index from your sitemap, generated at your own origin. Experimental, runs in the optimizer worker, off by default.
Read post →mod_pagespeed 2.1 ships an nginx Web Bot Auth verifier that checks RFC 9421 signatures and labels each request in $x_verified_bot. Observe-only, default off.
Read post →SSRF protection for headless rendering: the optimizer worker forces Chrome offline, routing subresources through an IP-pinned fetch re-checked per redirect.
Read post →Strip tracking parameters to stop cache fragmentation: mod_pagespeed 2.1 normalizes URLs before keying, dropping UTM params, sorting the query, aliasing hosts.
Read post →Default cache TTL when no Cache-Control: per-content-type heuristic TTLs, RFC 9111 Age adjustment, and the shared-vs-private cache split in mod_pagespeed 2.1.
Read post →Headless LCP and CLS measurement in mod_pagespeed 2.1: the optimizer worker's PerformanceObservers capture the LCP element and shifts to drive preloads.
Read post →How the mod_pagespeed 2.1 optimizer worker warms hot-URL caches: nginx flags a hot URL and the worker pre-builds the whole image variant matrix — format, viewport, density, Save-Data — instead of encoding one variant per request.
Read post →How a headless Chrome V8 coverage pass measures which JavaScript actually executes before first paint, so the mod_pagespeed 2.1 optimizer worker can safely defer the scripts that never run on load.
Read post →To minify JavaScript safely you have to parse it, not strip whitespace. How the mod_pagespeed 2.1 optimizer worker's tokenizer handles automatic semicolon insertion, regex-vs-divide, and a parse-error fail-safe that ships the original untouched.
Read post →How to serve markdown to AI crawlers on the same URL via Accept: text/markdown, synthesize /llms.txt from the sitemap, and honor AI opt-out directives.
Read post →How a proxy generates server-injected resource hints: speculation-rules prefetch derived from real traffic, priority-bucketed preconnect, font preload.
Read post →How mod_pagespeed 2.1 scores encoded images against a SSIMULACRA2 target in the optimizer worker and re-encodes until the result clears tolerance.
Read post →How cache key derivation in mod_pagespeed 2.1 hashes host plus URL into one key and scores stored variants in one selector pass instead of probing many keys.
Read post →Cache-Control safety in mod_pagespeed 2.1: why must-revalidate, not max-age, is the real safety net, and when aggressive TTLs with stale-if-error and stale-while-revalidate are the right call.
Read post →Conditional revalidation vs purge: when a 304 ETag round-trip beats PURGE and preserves optimized AVIF/WebP variants on an HTML-only deploy with no rebuild.
Read post →How critical CSS extraction works without a build step: the original beacon model, why CDNs broke it, and how 2.0 moved to heuristics + headless Chrome.
Read post →How mod_pagespeed 2.1 feeds the Chrome Coverage API critical CSS: the worker inlines cached stylesheets into a network-blocked sandbox to see real usage.
Read post →mod_pagespeed 2.1 keeps optimization work off the nginx request path with fire-and-forget IPC to the worker: a small notification, no reply, so a cache miss stays cheap and requests never wait on an encode.
Read post →Why flattening CSS @import rules is harder than concatenation: media intersection, @charset aborts, url() rebasing, and the CssFlattenMaxBytes cap.
Read post →Content-aware image optimization classifies decoded images and denoises noisy sources before encoding, so photos, screenshots, and logos get the right codec.
Read post →Does mod_pagespeed break a strict Content-Security-Policy? Where automatic rewriting collides with a CSP, feature by feature, and how the HonorCsp directive keeps optimized pages policy-compliant.
Read post →How the mod_pagespeed 2.1 optimizer worker precomputes 103 Early Hints preloads and lets nginx serve them from cache, using sentinel cache keys — the reserved Viewport=3 trick — to store them alongside per-URL content variants.
Read post →Purging one URL in mod_pagespeed 2.1 touches more than one cache entry. The fan-out problem, the lookup-time design 1.x used, and why the optimizer worker deletes immediately.
Read post →Raster to SVG auto-vectorization in mod_pagespeed 2.1: the optimizer worker traces logos and icons with VTracer, collapsing the variant matrix into one.
Read post →How the mod_pagespeed 2.1 optimizer worker hashes a page template so critical CSS is computed once and reused across every URL sharing that template, with analysis-queue dedup to skip redundant renders.
Read post →The mod_pagespeed 2.1 optimizer worker pixel-diffs the rendered above-fold before caching a headless critical-CSS variant. If the optimized page looks different, the gate discards it and keeps the heuristic version.
Read post →How a WordPress server-side page cache plugin sets Cache-Control on anonymous pages and purges the mod_pagespeed cache on publish, instead of caching in PHP.
Read post →Google's new Search Console AI performance report measures your visibility in AI Overviews and AI Mode, not how fast your pages load. The difference, explained.
Read post →AVIF beats WebP on size but is slower to encode. In 2026, serve AVIF, WebP, or the original per request off the Accept header instead of picking one format for everyone.
Read post →One perception-based quality knob; a trained model predicts the right JPEG, WebP, and AVIF encoding parameters per image in microseconds. No per-codec tuning, self-hosted.
Read post →A native nginx module that transcodes images to WebP and AVIF on serve, content-negotiates on Accept, and caches the variant. Install from signed apt/yum, no compiling.
Read post →Why upstream ngx_pagespeed won't compile on nginx 1.25+ (sys_siglist, glibc, OpenSSL 3, toolchain drift) — and the prebuilt module to install instead.
Read post →Reduce TTFB on nginx: split origin compute, network, and cache, then fix keep-alive, HTTP/2 or HTTP/3, TLS resumption, and variant-aware caching.
Read post →Image SaaS bills per transformation and per GB of egress. Self-hosted optimization transcodes WebP/AVIF on your own servers — no per-transformation cost, no third party.
Read post →A content hash in a .pagespeed. URL gives mod_pagespeed year-long caching with automatic cache busting — the same idea webpack contenthash and Cache-Control: immutable landed on later. Plus what data-pagespeed-url-hash actually is.
Read post →40% of the top 1,000 sites serve almost nothing to non-JavaScript AI crawlers — ChatGPT, Perplexity, and Claude see an empty page. The data, and how to fix it.
Read post →Serve WebP and AVIF from ASP.NET Core with no controller or Razor changes. WeAmp.PageSpeed middleware does Accept-header content negotiation, viewport sizing, and LCP preload.
Read post →How to fix INP on ASP.NET Core: Razor + jQuery responds well to bundling and the WeAmp.PageSpeed middleware; Blazor Server INP is architectural and needs WASM.
Read post →The dl-ssl.google.com mod_pagespeed .deb is Google's last stable build, 1.13.35.2 (2018), with years of unpatched CVEs. Get the maintained download for Apache, nginx, and IIS instead.
Read post →Yes, mod_pagespeed is deprecated: the 1.13.35.2 binaries run but haven't had security updates in years. What to use instead on Apache, nginx, IIS, and ASP.NET Core.
Read post →A working docker-compose.yml for ModPageSpeed 2.0 on nginx: worker + interceptor + shared Cyclone cache volume. Verify with curl, done.
Read post →Extract and inline critical CSS at the nginx layer for any backend (PHP, Rails, Django, ASP.NET, Go). No WordPress plugin. No headless browser. No Node build step.
Read post →How to fix CLS on ASP.NET Core: pre-size async view components, persist image dimensions, reserve banner space, rewrite img tags via middleware.
Read post →Fix Largest Contentful Paint on ASP.NET Core: async view components, immutable cache headers, deferred JS, and the WeAmp.PageSpeed middleware — for Razor Pages, MVC, and Blazor Server.
Read post →mod_pagespeed 1.15 ships 765 merges since 1.13.35.2: image-decoder hardening, a full sanitizer matrix, a current dependency graph, and the IIS port in the C++ tree.
Read post →How to fix INP on nginx: a CMS-agnostic guide. Server-layer JS minification helps if your JS is bloated; if your stack is already lean, the wins are upstream.
Read post →Fix Cumulative Layout Shift on nginx-served sites: rewrite img tags to add width/height with ngx_pagespeed (mod_pagespeed 2.1), add a CSS aspect-ratio backstop, and ship dimensions at build time.
Read post →How to fix LCP on nginx: HTTP/2, gzip_static, TLS resumption, and the mod_pagespeed rewriter. Stack-agnostic LCP fixes that work behind any backend in 2026.
Read post →Fixing INP on Magento 2: the interaction cost lives in KnockoutJS and RequireJS, so theme architecture (Hyvä) moves it, not a server rewriter — plus exactly what mod_pagespeed can and cannot do.
Read post →Fix Cumulative Layout Shift on Magento 2 product pages: stop Fotorama gallery jumps, pre-size the mini-cart and private-content blocks, and write img dimensions at the server layer.
Read post →How to fix LCP on Magento: tame the RequireJS waterfall, regenerate catalog images, inline critical CSS at the server. Step-by-step for Magento 2 in 2026.
Read post →How to fix INP on WooCommerce: server-layer JS minification reduces the parse cost, but cart and variation handlers are architectural.
Read post →How to fix CLS on WooCommerce: stop the gallery shift, lock variation swap dimensions, reserve cross-sell space, and rewrite img tags at the server.
Read post →Fix LCP on WooCommerce: shrink the product gallery, drop cart-fragments on non-shop pages, and rewrite catalog images at the server with mod_pagespeed.
Read post →How to fix INP on WordPress: diagnose the responsible interaction, defer non-critical JS at the server layer, then trim plugin handlers and jQuery.
Read post →How to fix CLS on WordPress: diagnose the shifts, set width/height on every image at the server layer, lock down fonts, reserve banner space.
Read post →How to fix LCP on WordPress: diagnose the hero, inline critical CSS at the server, convert JPEG to WebP, and verify in Search Console. Step-by-step, 2026.
Read post →Google mod_pagespeed and ngx_pagespeed are no longer actively developed. mod_pagespeed 2.1 is the maintained continuation. Here is how the paths compare.
Read post →Run the mod_pagespeed 2.1 optimization pipeline as ASP.NET Core middleware via NuGet — image transcoding, critical CSS and cache serving in two lines of C#.
Read post →Migrate from Google's mod_pagespeed 1.13.x or ngx_pagespeed to ModPageSpeed 2.0: directive mapping, Docker Compose setup, image-format checks, and a verification checklist.
Read post →How the mod_pagespeed 2.1 optimizer worker extracts and inlines critical CSS two ways: static heuristics in under 5ms on every page, plus an optional headless-Chrome path for true above-the-fold rules at First Contentful Paint.
Read post →Image CDNs run $35–$3,500/mo as traffic grows; self-hosted mod_pagespeed 2.1 stays flat. Break-even is ~100–170K requests/mo. Full 2026 cost model, no bandwidth fees.
Read post →How mod_pagespeed 2.1 reads the Save-Data request header to serve lighter image variants -- a 30-50% bandwidth cut stacked on top of format and viewport optimization.
Read post →Measured ModPageSpeed 2.0 results on e-commerce, blog, news, and portfolio sites: WebP/AVIF image savings and real LCP, FCP, CLS, and Lighthouse gains on 3G, 4G, and broadband.
Read post →Serve WebP and AVIF automatically on nginx, self-hosted. The mod_pagespeed 2.1 optimizer worker decodes each image once and generates up to 37 responsive variants across format, viewport, and pixel density.
Read post →The story behind ModPageSpeed 2.0 — why mod_pagespeed is no longer actively developed, what was kept from PSOL, and how a new architecture replaced the RewriteDriver.
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