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IISpeed reloaded: Announcing 1.1.0

We are happy to announce IISpeed 1.1.0, which brings cutting edge WPO technology to Microsoft's IIS web server. IISpeed 1.1 is build on top of Google's PageSpeed Optimization SDK v. 1.7

IISpeed 1.1.0 can be downloaded here.

New Features
  • prioritize_critical_css: Inline only the CSS used by the page.
  • convert_to_webp_lossless: Re-compresses GIF and PNG images to lossless WebP.
  • PageSpeed Console: The PageSpeed Console monitors your installation's performance and links to general information on how to improve the performance.
  • dedup_inlined_images: Filter that removes redundant inlined images and replaces them with JavaScript that loads all subsequent uses from the first.
  • Supporting downstream caches: Experimental feature for supporting caching proxy servers to allow HTML to be cached in these servers.
  • Randomly drop expensive rewrites: To reduce processing load, PageSpeed can be configured to optimize the most frequently fetched resources, leaving infrequently fetched resources alone. This is accomplished by randomly dropping expensive (CSS and image) rewrites. Frequently fetched resources will have a higher probability of being rewritten than infrequently fetched resources. Over time, frequently accessed resources will be optimized and cached so a page will be fully optimized. Infrequently accessed pages will be left unoptimized or partially optimized, saving CPU time and cache space.
  • DisableRewriteOnNoTransform: Default on, but may be turned off to allow PageSpeed to rewrite resources even if they have a Cache-Control: no-transform header.
  • Experimental Shared Memory Metadata Cache: An in-memory cache that shares metadata entries between IIS worker processes on the same server. This can provide significant performance benefits. 
  • Client Options Header: Support for a new request header that can be used to configure image optimizations.
  • Lossless & transparent WebP support: PageSpeed can now take advantage of support for lossless & transparent WebP images in some newer browsers, which can provide smaller file sizes than PNG.
  • Embedding configuration into resource URLs: You can now configure PageSpeed to embed image & CSS optimization settings in resource URLs. This is useful in multi-server setups where perfectly replicating configuration information may be infeasible.
  • Better CDN support in MapProxyDomain: You can now optionally provide a third argument to MapProxyDomain in order to use a domains of a separate hosting site for optimized resources being proxied.
  • IE6/IE7 support in lazy load images: The lazy load images filter now also applies for visitors using Internet Explorer versions 6 and 7.
  • Support for HTTPS fetching
  • Updated library for the cannonicalize javascript filter
  • Supports reloading all settings (including root settings) on the fly
  • Now uses beaconing to determine content that should be prioritized (prioritize_critical_css, lazyload_images)
  • Simplified, single installer for 32 and 64 bits platforms.

New Configuration Options

  • CriticalImagesBeaconEnabled
  • JpegNumProgressiveScans
  • JpegNumProgressiveScansForSmallScreens
  • WebpRecompressionQuality
  • WebpRecompressionQualityForSmallScreens

Configuration defaults updated

Starting in this release, we enable lossy image compression by default and update several other default configurations values. Updates:

  • Default AvoidRenamingIntrospectiveJavascript to on (was off).
  • Default ImageInlineMaxBytes to 3072 (was 2048).
  • Default CssImageInlineMaxBytes to 0 (was 2048).
  • Default MaxInlinedPreviewImagesIndex to -1 = unlimited (was 5).
  • Default MinImageSizeLowResolutionBytes to 3072 (was 1024).
  • Default ImageRecompressionQuality to 85 (was -1 = lossless).
  • Default JpegRecompressionQualityForSmallScreens to 70 (was -1 = lossless).
  • Default WebpRecompressionQuality to 80 (was -1 = lossless).
  • Default WebpRecompressionQualityForSmallScreens to 70 (was -1 = lossless).
  • Defaults to creating a filesystem cache in the temp directory when none is configured as a L2 to the LRU.

Changes to Configuration Options

  • IISpeed AddOptionsToUrls added
  • 3-argument version of IISpeed MapProxyDomain added
  • IISpeed BeaconUrl arguments no longer required to end in ?ets=


Compiled from the mod_pagespeed changelists - we will be updating this list shortly, as it is not exhaustive at this moment.
  • Issue 199 Multiple references to the same small images all get inlined.
  • Issue 644 Improve lazyload behavior.
  • Issue 675 rewrite_javascript breaks Wordpress /wp-admin/ pages with certain common WP plugins.
  • Issue 683 Don't strip Cache-Control:no-store, etc. headers.
  • Issue 684 elide_attributes should not remove type=text as wordpress uses it in CSS.
  • Issue 690 Add originating page URL query-param to beacon URL.
  • Issue 700 Image height tag removed when image is embedded.
  • Issue 707 PageSpeed lost img tag src value when too busy.
  • Issue 709 combine_javascript will kill defer_javascript's pagespeed_no_defer attribute.
  • Issue 719 Support random dropping of expensive rewrites.
  • Issue 721 New default values for PSOL options.
  • Issue 722 rewrite_css should not apply to files with an @import in the middle.
  • Issue 284 Default FileCacheInodeLimit to 500000 and AvoidRenamingIntrospectiveJavascript to on as in mod_pagespeed.
  • Issue 321 The Connection, Vary, Keep-Alive, Transfer-Encoding, and Server headers would sometimes be duplicated.
  • Issue 323 Beacons were being served without cache-control headers.
  • Issue 508 Large numbers get rewritten to scientific notation.
  • Issue 609 MapProxyDomain does not proxy non-optimized resources
  • Issue 615 Rewriting domains does not work with PageSpeedMapProxyDomain
  • Issue 629 insert_image_dimensions on -elements causing invalid document
  • Issue 630 CSS parser incorrectly parses "1.em" as "1em"
  • Issue 649 defer_javascript and defer_iframes not turned on for Mobile
  • Issue 650 Images inlined for CSS inlines in HTML even when CssImageInlineMaxBytes is zero
  • Issue 652 Last-Modified header should not be stripped with ...
  • Issue 648 Combine_css and combine_javascript loses subdirectories occasionally
  • Issue 641 Lazyload Images Defect on Blackberry Browser w/ OS <= 5
  • Issue 322 We should not rewrite <img src=... width=1 height=1> to 1x1
  • Issue 581 lazyload_images should be enabled for IE6/IE7
  • Issue 587 Pagespeed should respect Cache-Control: no-transform
  • Issue 591 File cache cleaner improperly removing lock files
  • Issue 599 Support MapProxyDomain to CDN
  • Issue 600 Proxied resources aren't combined with local resources
  • Issue 601 InitializeNested in CssHierarchy initializes a StringPiece with too wide a scope
  • Issue 608 PageSpeed=off with no filecachepath causes problems with .pagespeed. resources
  • Issue 614 CSS: minify 0.25 -> .25

New free mode

When unregistered, IISpeed 1.1 appends a small 'Powered by IISpeed' banner to the bottom of your website. Your are allowed to run it for free and as long as you want that way, on any domain (as long as the banner is visible). Buying a license will remove the banner.

Otto van der Schaaf
IISpeed team

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