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Recent versions of Firefox create a shader-cache folder within each Firefox profile.

Some privacy applications automatically delete this folder as part of their cleanup routines.

Can Firefox's shader-cache folders contain any private data, and if so, what?

RockPaperLz- Mask it or Casket
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1 Answers1

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Shaders are most commonly used to produce lit and shadowed areas in the rendering of 3D models. They are downloaded from websites that do such rendering and are cached by the browser to optimize future loads.

Privacy issues may arise as caching could help fingerprint the user, by his cached shaders. Also, if shaderA is used and cached when visiting siteA.com, then performance differences could possibly be used to detect whether the user has visited that site before.

These extremely vague privacy concerns are (in my opinion) overdoing privacy, as there are so many easier methods to fingerprint a user, see the post Unique Browser / User ID.

Removing the shaders cache should in general not cause any big problem, as the shader will be downloaded the next time you visit the website. For large shaders, this can slow down appreciably your first access to the website, while the shader is downloading and being setup.

harrymc
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    Thanks Harry. I appreciate your knowledge. I rarely visit any websites that contain any obvious 3D content (games, etc.), so I ran a test. Upon simply opening Firefox with a *brand new* browser profile, many `shader-cache` files are created. So I think we need a good definition of what is considered "3D". Also, I wonder (aloud) if shaders could actually be used as a very efficient and accurate fingerprinting method. I'm not sure if the browser developers have accounted for that possibility. Besides fingerprinting, what about the shader cache files themselves containing private data? – RockPaperLz- Mask it or Casket May 26 '21 at 03:58
  • Shaders are also installed by the browser itself, and this area is still in evolution. Deleting them shouldn't cause a problem. – harrymc May 26 '21 at 06:57
  • What are the purpose of the shaders installed by the browser itself? AFAIK, the browser itself doesn't have any true 3D UI elements. Regardless, yes, there is no problem with deleting them... I tried it, and everything still looked good. – RockPaperLz- Mask it or Casket May 26 '21 at 15:00
  • Firefox is now moving to include them in the installation. It's perhaps motivated by gaming support: https://developer.mozilla.org/en-US/docs/Games/Techniques/3D_on_the_web/GLSL_Shaders. – harrymc May 26 '21 at 15:04
  • Thanks for the link. My favourite line in it: *GLSL is not as intuitive as JavaScript.* LOL. ;) – RockPaperLz- Mask it or Casket May 26 '21 at 15:06
  • Your answer is definitely helpful and much appreciated! :) The big question not addressed by it is if the shader cache can contain any private data within its constituent files. I'm interested in learning the answer to that question. – RockPaperLz- Mask it or Casket May 26 '21 at 15:14
  • As far as I know the answer is that it has no private data, but only may point to the user's habits and websites he visits, especially if he plays 3D browser games. This is different, of course, if you are a game developer and you created these shaders yourself. – harrymc May 26 '21 at 15:17