The ETAg — entity tag — is an internet cache validation technique that net servers use for figuring out sources. The core concept behind the characteristic is to make use of it to match sources to find out whether or not they’re equivalent or not.

As is the case with many Net options these days, they can be utilized for good and unhealthy. ETAgs are used within the HTTP header which implies that they can be utilized even when the browser rejects JavaScript, cookies or native storage.

Tip: We talked about ETAg monitoring again in 2014, and talked about it again in 2010 within the Evercookie article as properly.

Again in 2011, researchers at UC Berkely found that web sites have been utilizing ETAgs for monitoring functions. ETAgs are cached by the browser, and returned by the browser to the online server when a useful resource is requested once more. Using ETAgs allowed websites to trace customers throughout classes, no matter whether or not they modified their IP addresses, allowed cookies and JavaScript, allowed the storing of content material on the native system, or had plugins enabled.

Clearing the online browser cache ought to take away ETAgs.  Pants, who created the Ghacks person.js file, found a while in the past that this was not the case in Firefox. He observed that Firefox was not deleting ETAg knowledge anymore when she cleared the cache of the browser, one thing that Firefox did earlier than that point.

She makes use of reminiscence solely caching on her system, and came upon that disabling each caches (reminiscence and disk) would defeat ETAgs however that it had different penalties on the similar time.

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Earthling, one other vivid thoughts behind the Ghacks person.js file, discovered a greater answer. Since ETAgs are set in headers, manipulating headers accountable will do the trick.

  1. You do must obtain and set up the Header Editor extension that’s obtainable on Mozilla AMO for that although.
  2. After getting it put in, click on on the extension’s icon to open the editor.
  3. Click on on Add so as to add a brand new rule, and fill out the next fields:
  4. Title: ETAg Removing
  5. Rule Sort: Modify the response header (this modifications the fields).
  6. Execute sort: regular
  7. Header identify: etag
  8. Click on on the Save button to avoid wasting the brand new rule.

You’ll be able to take a look at this on the cookieless cookies web site to check this (with and with out the header manipulation).

Notice that this bug is particular to Firefox. It could even be a difficulty in Firefox-based browsers.

Closing Phrases

It’s unclear when Firefox stopped eradicating ETAgs when clearing the browser cache, solely that that is the established order proper now. A bug itemizing on [email protected] that was created 14 years in the past highlights the monitoring problem related to ETAgs.

About Martin Brinkmann

Martin Brinkmann is a journalist from Germany who based Ghacks Know-how Information Again in 2005. He’s captivated with all issues tech and is aware of the Web and computer systems just like the again of his hand.

You’ll be able to comply with Martin on Fb, Twitter or Google+