The current reality is that there are *two branches*, not an official one and a lesser one. I keep developing my branch the same way and in the same spirit I have since [the beginning of uBlock in June 23, 2014](http://www.wilderssecurity.com/threads/ublock-a-lean-and-fast-blocker.365273/).
You are more likely than anywhere else to find a neutral explanation in this [Wikipedia article](http://en.wikipedia.org/wiki/UBlock) for the differences in features between uBlock Origin and uBlock.
uBlock Origin (or uBlock₀) is not an *ad blocker*; it's a general-purpose blocker. uBlock₀ blocks ads through its support of the [Adblock Plus filter syntax](https://adblockplus.org/en/filters). uBlock₀ [extends](https://github.com/gorhill/uBlock/wiki/Filter-syntax-extensions) the syntax and is designed to work with custom rules and filters.
That said, it's important to note that using a blocker is **NOT** [theft](https://twitter.com/LeaVerou/status/518154828166725632). Don't fall for this creepy idea. The _ultimate_ logical consequence of `blocking = theft` is the criminalisation of the inalienable right to privacy.
Ads, "unintrusive" or not, are just the visible portions of privacy-invading apparatus entering your browser when you visit most sites nowadays. **uBlock₀'s main goal is to help users neutralize such privacy-invading apparatus** — in a way that welcomes those users who don't wish to use more technical, involved means (such as [µMatrix](https://github.com/gorhill/uMatrix)).
_EasyList_, _Peter Lowe's Adservers_, _EasyPrivacy_ and _Malware domains_ are enabled by default when you install uBlock₀. Many more lists are readily available to block trackers, analytics, and more. Hosts files are also supported.
Once you install uBlock₀, you may easily un-select any of the pre-selected filter lists if you think uBlock₀ blocks too much. For reference, Adblock Plus installs with only _EasyList_ enabled by default.
For advanced usage, read about [dynamic filtering](https://github.com/gorhill/uBlock/wiki/Dynamic-filtering:-quick-guide) and more on [uBlock₀'s wiki](https://github.com/gorhill/uBlock/wiki).
<sup>[1] Details of the benchmark available at <ahref="https://github.com/gorhill/uBlock/wiki/Firefox-version:-benchmarking-memory-footprint">Firefox version: benchmarking memory footprint</a>.</sup><br>
<sup>[2] Important note: There is currently a [bug in Chromium 39+ which causes a new memory leak each time the popup UI of an extension is opened](https://code.google.com/p/chromium/issues/detail?id=441500). This affects <i>all</i> extensions. Keep this in mind when measuring Chromium's memory usage. In the benchmarks, I avoided opening the popups completely.</sup><br>
<sup>Details of the benchmark available in <ahref="https://github.com/gorhill/uBlock/blob/master/doc/benchmarks/cpu-usage-overall-20141226.ods">this LibreOffice spreadsheet</a>.</sup>
You can install the latest version [manually](https://github.com/gorhill/uBlock/tree/master/dist#install), from the [Chrome Store](https://chrome.google.com/webstore/detail/ublock-origin/cjpalhdlnbpafiamejdnhcphjbkeiagm), or from the [Opera store](https://addons.opera.com/en-gb/extensions/details/ublock/).
Alternatively, you can install [chrisaljoudi/uBlock](https://github.com/chrisaljoudi/uBlock) from [Chrome store](https://chrome.google.com/webstore/detail/ublock/epcnnfbjfcgphgdmggkamkmgojdagdnn). Slightly different feature set, same performance.
[Firefox Add-ons web site](https://addons.mozilla.org/firefox/addon/ublock-origin/), or install manually by downloading the latest [uBlock0.firefox.xpi](https://github.com/gorhill/uBlock/releases) file, and by dragging the downloaded `xpi` file to your add-on page.
Alternatively, you can install [chrisaljoudi/uBlock](https://github.com/chrisaljoudi/uBlock) from [Firefox Add-ons homepage](https://addons.mozilla.org/firefox/addon/ublock/). Slightly different feature set, same performance, proper support for legacy Firefox-based browsers.
For Firefox legacy versions -- prior to Firefox 29 -- it is best to install [chrisaljoudi/uBlock](https://github.com/chrisaljoudi/uBlock) as it has official support for legacy Firefox versions.
To benefit from uBlock Origin's higher efficiency, it's advised that you don't use other inefficient blockers at the same time (such as AdBlock or Adblock Plus). uBlock₀ will do [as well or better](#blocking) than most popular ad blockers.
