CODEWITHSUNDEEP
iiscompressiongzipiis-8.5content-encoding
user3621633
user3621633

Reputation: 1721

IIS 8.5 Static Compression missing Content-Encoding response header, yet Failed Request Tracing shows compression with gzip

I observed that Content-Encoded response header was missing, notably Content-Encoded: gzip. I'm using static content compression. The dynamic content compression feature was never installed. I installed it, enabled it, and tested again. This time, Content-Encoded: gzip appeared in the response. The question is why does the response header appear for dynamic content compression but not for static content compression? I'm fairly certain that IIS is applying gzip to static content compression. Here's why:

  1. I have an IIS URL Rewrite outbound rule which modifies the response on an HTML page. The outbound rule yielded Error 500.52, URL Rewrite Module error -- Outbound rewrite rules cannot be applied when the content of the HTTP response is encoded ("gzip"). The rule is not the issue, just evidence that gzip is reportedly being applied. I disabled the rule. That's clue #1.

  2. Clue #2 is I enabled Failed Request Tracing and observed that not only static compression was being applied but the StaticFileModule was storing the compressed file in the following location: C:\INETPUB\TEMP\IIS TEMPORARY COMPRESSED FILES\MY WEBSITE\$^_GZIP_D^\INETPUB\WWWROOT\TEST.HTML.

I read the Microsoft document on IIS HTTP Compression and--I could be wrong--I didn't see any language that suggests gzip can be employed with static compression. Based on the two clues above, gzip is being employed with static compression.

So I go back to the original problem, which is Content-Encoded response header is missing for static content impression, yet evidence suggests that IIS is not only compressing static content but compressing it with gzip. Is this simply a bug? Is this by design?

Upvotes: 0

Views: 546

Answers (1)

Jokies Ding
Jokies Ding

Reputation: 3494

Static Compression will add Content-Encoded header when it work.

If you enable failed request tracing and trace static compression module. You will see this.

enter image description here

It means static compression won't work if a static file didn't get hit frequently.

If you relay this request doezens times. Then you will see that header.

enter image description here

Be careful that, there is a limit for minimum file size for compression. You could modify that value in IIS manager->server node->configuration manager->system.webServer/httpCompression->minfileforcomp

enter image description here

Upvotes: 1

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