Services
Technology Web App Development Mobile App Development Windows App Development Database Development UI/UX Development Cloud Development SEO Digital Marketing Guest Posting Content Writing Artificial Intelligence Data Science ERP Development CRM Development CMS Development LMS Development Business Listing Blockchain Technology Startup Promotion AI Tools Integration
Products
Data Converter Cleaner TUC - Unit Converter Import Export Survey Manager Tweet Controller
Developer
Article Blog Forum Interview Beginner News Startup Quiz
Users
Career
Apply Job Internship
Pricing
Login Sign Up Get a Quote

interview

Home Interviews How to enable ETag support for static content (CSS, JS, images, etc.) – MindStick
Ask Question

1 Answers

ICSM Computer
ICSM Computer 05 Aug 2025
Report Abuse

1. ETag Support is Handled Automatically by IIS

For static files, IIS automatically generates ETags based on file metadata (like last modified date and file size).
However, you can control behavior and enhance caching using web.config.

2. Enable/Disable ETags via IIS Settings

IIS adds headers like:

ETag: "6396c9a2b1d6d81:0"
Last-Modified: Wed, 06 Aug 2025 06:30:00 GMT

These are enabled by default unless removed via custom headers.

3. Control Cache for Static Content in web.config

You can’t directly configure ETag values in web.config, but you can combine ETag behavior with long-term caching:

Example: Cache Static Files + Let IIS Handle ETag

<configuration>
  <system.webServer>
    <staticContent>
      <clientCache cacheControlMode="UseMaxAge" cacheControlMaxAge="365.00:00:00" />
    </staticContent>
  </system.webServer>
</configuration>

This will:

  • Add Cache-Control: public, max-age=...
  • Keep ETag behavior managed by IIS

4. Disable ETag (Optional)

If you want to remove ETags (for performance tuning or to rely only on Cache-Control):

In web.config

<configuration>
  <system.webServer>
    <httpProtocol>
      <customHeaders>
        <remove name="ETag" />
      </customHeaders>
    </httpProtocol>
  </system.webServer>
</configuration>

⚠️ This removes the ETag header from the response — not recommended unless you're managing cache manually.

5. Advanced (Optional): Use Versioned URLs Instead

Another best practice is to use query string versioning or fingerprinted file names:

<!-- Better cache busting with versioned links -->
<link rel="stylesheet" href="/css/site.css?v=20250806" />

This makes the browser treat the URL as a "new" file if the version changes, avoiding reliance on ETag entirely.

Summary

Goal How
Enable ETag for static files IIS does this by default
Control cache duration Use <clientCache> in web.config
Disable ETag Remove ETag header via customHeaders
Version cache manually Use versioned URLs (?v=...) in your markup
advertising
Markdown for AI

A clean, structured version of this page for AI assistants and LLMs.

Open .md