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How to block base64 images with uBlock (and other things)

Some websites are really imaginative to try and bypass ad-blockers. Although their methods are interesting to study sometimes, usually when sites bother placing anti-ad-blocking code they tend to use it to place particularly annoying things.

One site I visit sometimes uses quite a dirty method: they place all ad images _inline_, as base64 encoded data.
I don’t think any uBlock filter catches those, as it would require site-specific filters instead of the usual advertising network-specific ones. However, you can easily make a filter yourself. Go to uBlock options (if you don’t know where to find them, click the uBlock icon to pop up the uBlock GUI then click the tiny cog in the top-left corner – yes I had a hard time finding it too a long time ago :s), then to the My filters tab. And add a line like:

example.com##img[src^="data:"]

And that’s all (make sure you replace example.com with your target site, of course). Just hit “Apply changes”, and when you reload the site the base64 images should be gone.

While I’m at it, here is some more useful filter syntax:

example.com

=> blocks a whole domain name. Useful to block an advertising network that isn’t supported yet in the published filters. Or also to block a site without installing a specific add-on such as BlockSite

example.com##.some-class

=> blocks all elements of class “some-class”.

example.com###some-id

=> blocks all elements of ID “some-id” (well, normally IDs should be unique so that would be only 1 element).

example.com##script:contains(sendAdBlockEventGA)

=> blocks script that contain the keyword “sendAdBlockEventGA”. I’m not really sure of the extent of what is blocked (just the line around the detected word, I assume?), and also maybe this only works on Firefox. Well, long story short that’s not a filter I actively use at the moment, but still I suppose it can be useful for instance to block those big fat popups saying “HEY YOU PLEASE TURN OFF THAT ADBLOCKER”. Yup, I should definitely try to remember to give it a spin next time I see one of those 😉

Posted in privacy.


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