IEInternals

A look at Internet Explorer from the inside out. @EricLaw left Microsoft in 2012, but was named an IE MVP in '13 & an IE userAgent (http://useragents.ie) in '14

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  • Blog Post: Managed Code Browser Extensions

    I love the .NET Framework. I’ve been programming in C# since 2001, I spent much of my free time for a decade building Fiddler on .NET, and I now code in C# for a living. .NET provides a fantastic, highly-productive platform suitable for building a huge range of tools and applications, and as it...
  • Blog Post: Braindump: DNS

    Note: The “brain dump” series is akin to what the support.microsoft.com team calls “Fast Publish” articles—namely, things that are published quickly, without the usual level of polish, triple-checking, etc. I expect that these posts will contain errors, but I also expect...
  • Blog Post: Networking Improvements in IE10 and Windows 8

    Internet Explorer 10’s networking code builds upon the performance improvements in IE9 ( caching , overall networking ) to help ensure that IE10 loads pages as quickly as possible. In IE10, we identified a few key areas for improvement based on customer feedback, code inspection, and telemetry...
  • Blog Post: Please Stop Polluting

    When I surf the web, I almost always have Fiddler running, and as a consequence I see a lot of “hidden” pollution in pages. Much of this cruft has built up over the years, copied from site to site, probably with little critical thought about its necessity. Please remove any META tags you...
  • Blog Post: Use IMG tags only for Images

    First, a bit of background. When web developers are optimizing the performance of their sites, often they try to use their homepage to pre-cache resources that will be used on later pages. They might do so by kicking off "pre-fetch" resource downloads after the content required by the homepage itself...
  • Blog Post: Best Practice: Get your HEAD in order

    To ensure optimal performance and reliability when rendering pages, you should order the elements within the HEAD element carefully. First, I’ll explain the optimal order, and then explain the reasoning for this structure. Optimal Head Ordering <doctype> <html> <head>...
  • Blog Post: Integrated Windows Authentication

    Inside Internet Explorer’s Tools > Internet Options > Advanced dialog, there’s an option named Enable Integrated Windows Authentication : This preference is stored using a REG_DWORD named EnableNegotiate inside HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings...
  • Blog Post: Understanding Once-Per-Session Cache Validation

    Last year, I wrote about the IE9 improvements in heuristic expiration , which apply when a server fails to specify how long a cached resource should be treated as fresh. Heuristic Expiration works by calculating an implicit freshness lifetime from the Last-Modified timestamp on the cached resource and...
  • Blog Post: HTTPS and Keep-Alive Connections

    As we explore network performance on the “real-world web”, one bad pattern in particular keeps recurring, and it’s not something that our many IE9 Networking Performance Improvements alone will resolve. The bad pattern is the use of Connection: close semantics for HTTPS connections...
  • Blog Post: What is msimgsiz.dat?

    Inside your Temporary Internet Files folder you likely have a file named msimgsiz.dat . If you open this file, you’ll find that it contains nothing but binary goo: Over the years, many people have asked or speculated about what this file is used for, and the answer is actually quite simple...
  • Blog Post: Understanding the IE9 Software Rendering Mode

    I recently heard from some users who are seeing lower-than-expected scores on the Speed Reading and FishIE Tank benchmarks. I went to check these tests myself and found that my laptop’s score was low. In fact, it was much lower than I’d seen last year. What happened? First, a bit of background...
  • Blog Post: Challenge-Response Authentication and Zero-Length Posts

    From time-to-time, web developers contact the IE team reporting that they’ve encountered a problem whereby Internet Explorer submits a POST but fails to transmit the content body. This bodyless POST indicates via the Content-Length header that the POST is zero-bytes long, regardless of how much...
  • Blog Post: Trivia: Animated GIF Timing

    Every now and again, someone reports that Internet Explorer is "slow" when rendering an animated GIF file. Typically, they'll load a lengthy animation in Firefox and IE and note that it runs much more quickly in Firefox. Similarly, Chrome and Safari are "slow" while Opera is "fast." Conversely, there...
  • Blog Post: The Performance Impact of META REFRESH

    Some sites will utilize the META REFRESH directive to perform a client-side redirection. In general, this should be avoided in favor of other redirection types, for instance, a server-side redirection (HTTP/3xx) or by using JavaScript. Using META REFRESH creates a potential performance problem in IE...
  • Blog Post: HTTPS Caching and Internet Explorer

    From time-to-time, I get questions about Internet Explorer’s behavior when it comes to caching of HTTPS-delivered content. It comes as a surprise to many that by-default, all versions of Internet Explorer will cache HTTPS content so long as the caching headers allow it . If a resource is sent...
  • Blog Post: IE8 Lookahead Downloader Fixed

    Background Last year, I wrote about two bugs in IE8’s Lookahead Downloader that would cause IE8 to make spurious download requests for non-existent URLs. These spurious download requests generally went unnoticed by users, because the main parser would eventually retrieve the correct resource when it...
  • Blog Post: Use Sensible Long-Lived Cache headers

    As some of you might expect, I watch all of my network traffic when I browse the web—you never know when you’ll see something interesting. This afternoon, for example, my curiosity was piqued when I noted that as I browsed around the Zune website, my browser issued conditional HTTP requests...
  • Blog Post: Microsoft Doloto Performance Optimization Tool

    Ben Livshits and Emre Kiciman of Microsoft Research have released the Doloto performance-optimization tool . This cool tool enables web developers to optimize page-load time by ensuring that pages only pull in the JavaScript functions they need. Mentioned in Steve Souder's Even Faster Web Sites earlier...
  • Blog Post: Bugs in IE8's Lookahead Downloader

    All bugs mentioned in this post are now fixed . Internet Explorer has a number of features designed to render pages more quickly. One of these features is called the "Lookahead Downloader" and it's used to quickly scan the page as it comes in, looking for the URLs of resources which will be needed...
  • Blog Post: Unshackling IE8 Performance

    In general, IE8 is a significantly faster browser than prior versions. We made a number of major investments throughout the browser’s code to help ensure that IE users will have a great real-world experience on the web. However, it is definitely the case that some users are experiencing abnormal and...
  • Blog Post: Internet Explorer's Cache-Control Extensions

    Some time ago, I wrote a summary of how Internet Explorer’s cache works . At the time, I left out mention of the two cache-control directives introduced by IE5: pre-check and post-check . These directives enable a “background update” mechanism where a cached resource is reused while...
  • Blog Post: Vary with Care

    About the Vary Response Header As described in the HTTP/1.1 specification ( RFC2616 ), the Vary response header allows a cache to determine if a cached (still fresh) response may be returned for a subsequent request, based on whether or not the new request's headers match those that were sent when...
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