Guide:Blocking ads

TLDR: Use uBlock Origin

Adblocking is the act of choosing what content is displayed to you, and it's associated code executed, when using internet and consuming content, most commonly taking form of blocking ads and trackers which follow you across the web and sell your personal information to the highest bidder.
Most ads and ad companies are fundamentally opposed to privacy, as they have unilaterally decided that they are entitled to personal information about you which you would rarely volunteer if the method of gathering was less opaque. They further take it upon themselves to use this information against your personal interests, by manipulating your choices and taking away your freedom, to pad their bottom line.

Wait, isn't this hurting content creators?

Fundamental premise of such questions is that good or useful content would not exist unless it is commercially motivated. We fundamentally reject this idea. Have you seen Wikipedia?

We do too, Library Owl. We do too.

We believe that culture is and should be free (as in freedom), and the only real way to control information is to not disclose it. If you have made content publicly accessible on the web, then the content if freely accessible, and you don't get to decide how it is displayed by the reader.
Imagine if magazine publishers made their products available for free, but then tried to prevent you from tearing out the full page ads because it hurts their bottom line. Then imagine if those same magazines came with little cameras spying on you and with embedded GPS trackers, and you'd have the basic idea of what is being suggested here.
Publishers can put their content behind login screens and pay walls, and many do. They can refuse the serve the page unless the ads load. But they don't want to because it hurts their reach and search rank placement. Do not accept such attempts to moralise their way to even larger profits from people who will readily breach your privacy and serve you malware.

In the world where every page load assaults you with concentrated attempts to control your mind and decisions it makes (which do work, regardless of how much you think they don't), blocking ads is the right thing to do.

Why block ads?

Most ads found online actively harm your privacy by both collecting information on you and using previously collected information about you to exert control over your decisions.

Collecting new information

Many websites, dare we say even most websites, embed into their code a tracking script which collects information about you upon the page load. The culprits are often the usual suspects such as Google, Facebook, Amazon or Microsoft, who have programs which allow website creators the ability to display ads in return for revenue as well as insight into the website's user base. While the webmaster may use this info to improve their website, the advertising company feeds this data into their machine learning engines which correlate this data to infer, usually with a scary degree of accuracy, information about the website visitor.
Upwards of 200 parameters are tracked, but some of the most common ones are

• User agent - a sort of an ID string which tells the site the type of content the browser is likely to be able to render properly
• IP address - your internet address, which reveals your rough location (such as city or suburb you're in)
• Screen resolution - size/shape of your monitor
• HTTP cookies - small bits of unique text which sites leave behind on your device, allowing them to read it later on subsequent loads of the site
• Operating system - what type of device you're using
• system language

and many many others... While these bits of information seem inconsequential, a combination of 200+ such bits of information can uniquely identify you as an individual and allow the advertisers to build profile on you, a sort of permanent record, containing detailed records regarding who you are and what you like. This may include things you don't mind being made public, such as 'likes chocolate' but can also contain data that advertiser has inferred about you which may not be willing to share such as 'is gay' or 'is an atheist' (a capital crime in Saudi Arabia).
In this particularly depressing example, users on reddit are sharing tips on how to avoid being re-traumatised by ads following a miscarriage.