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uBlock Origin

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uBlock Origin
Original authorRaymond Hill (gorhill)
DevelopersCurrent:
Raymond Hill
Past:
Deathamns, Chris Aljoudi, Alex Vallat[1]
ReleaseJune 23, 2014; 12 years ago (2014-06-23)[2]
Stable release
1.73.0[3] / 5 August 2026; 9 days ago (5 August 2026)
Written inJavaScript
Operating systemCross-platform
PredecessorHTTP Switchboard and uMatrix
Available in72[4] languages
TypeBrowser extension
LicenseGPLv3
Repository

uBlock Origin (/ˈjuːblɒk/ YOO-blok[5]) is a free and open-source browser extension for content filtering, including ad blocking. The extension is available for Firefox and Chromium-based browsers (such as Chrome, Edge, Brave, and Opera).

uBlock Origin is actively developed and maintained by its creator and lead developer Raymond Hill and the open source community.[1] As of June 2026, the Chrome version of uBlock Origin had over 29 million active users and the Firefox version has over 10.6 million active users, making it the most popular extension on Firefox.[6][7]

History

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The development of uBlock Origin (uBO) came about by forking the codebase of HTTP Switchboard, an extension designed to give users control over browser requests. uBlock, which was the predecessor of uBlock Origin, was further influenced by uMatrix, another browser extension created by forking HTTP Switchboard.[8]

HTTP Switchboard

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HTTP Switchboard was initially released on September 20, 2013.[9][10][11][12][13][14] It enabled users to control the types of requests made by their browser, providing a way to block specific types of web content. However, development of HTTP Switchboard ceased on May 18, 2015.[15][16]

uMatrix

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In anticipation of the end of HTTP Switchboard's development, uMatrix was introduced on October 24, 2014.[17][8][18] This extension was designed for advanced users and acted as a request firewall, allowing users to control browser requests across two main dimensions: the domains and subdomains to which requests were sent, and the types of requests (such as cookies, images, XMLHttpRequest, frames, and scripts). uMatrix retained much of the user interface from HTTP Switchboard, but significantly expanded its functionality, offering a more granular level of control over web requests.

In a public discussion on August 2, 2020, lead developer Raymond Hill stated that he lacked time to work on uMatrix because it was "a project large enough that [he] would be able to work on it only if [he] wasn't working on uBO." In response to a further comment, Hill stated he would never pass development to anyone after past experience, giving concerns such as monetisation and feature bloat, and he would instead "at most" archive it, offering others the chance to fork the project.[19]

Development of uMatrix ended on July 21, 2021, without announcement, with the project's GitHub repository being converted to a public archive.

uBlock

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uBlock[note 1] was developed by Raymond Hill to use community-maintained block lists,[20] while adding features and raising the code quality to release standards.[21] First released in June 2014 as a Chrome and Opera extension, in 2015 the extension became available in other browsers.[citation needed]

A joint Sourcepoint and comScore survey reported an 833% growth from November 2014 to August 2015, the strongest growth among adblockers listed.[22] The report attributed the growth to the desire of users for pure blockers, outside the "acceptable ads" program operated by Adblock Plus.[23]

The development of uBlock stopped in August 2015 after its April break with uBlock Origin but there were updates again starting in January 2017.[24]

In July 2018, ublock.org was acquired by AdBlock and they resumed development.[25] From February 2019, uBlock began allowing users to participate in "acceptable ads",[26][27] a program run by Adblock Plus that allows some ads deemed "acceptable" and nonintrusive, and for which larger publishers pay a fee.[28]

uBlock Origin

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On April 3, 2015, Raymond Hill transferred the uBlock project to Chris Aljoudi due to frustrations with managing increasing user requests.[29] Hill explained that it was no longer a hobby: "These projects are to me, not a full-time job. It stopped being a hobby when it felt more and more like a tedious job. I will keep maintaining my version (and share with whoever cares to use it) because it guarantees the tool will match what I want out of it."[30] On April 6, Hill created his own fork of the project, naming it uBlock Origin.[31]

Since October 2017, uBlock Origin has been completely separated from Aljoudi's uBlock.[32] Aljoudi created ublock.org to host and promote uBlock and to request donations. In response, Hill stated that "the donations sought by ublock.org are not benefiting any of those who contributed most to create uBlock Origin."[33]

Features

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Blocking and filtering

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uBlock Origin supports the majority of Adblock Plus's filter syntax. The popular filter lists EasyList and EasyPrivacy are enabled by default. The extensions are capable of importing hosts files and a number of community-maintained lists are available at installation. Among the host files available, Peter Lowe's ad servers & tracking list and lists of malware domains such as uBlock Origin's own anti-malicious filter called Badware risks are also enabled as default, preventing users from visiting malicious websites such as those used for phishing, scams, malware, and more.[34] Some additional features include dynamic filtering of scripts and iframes and a tool for webpage element hiding.[citation needed]

uBlock Origin supports multiple improvements over the original uBlock, such as color vision deficiency mode, a DOM inspector, and dynamic URL filtering. [citation needed]

There used to be a feature that protected against IP address leaks via WebRTC. However, this feature was removed in version 1.38 for all platforms except Android, as most browsers no longer have vulnerabilities related to WebRTC leaks.[35]

Site-specific switches to toggle the blocking of pop-ups, strict domain blocking, cosmetic filtering, blocking remote fonts, and JavaScript disabling were also added to uBlock Origin.[36] The Firefox version of uBlock Origin has an extra feature which helps to foil attempts by web sites to circumvent blockers.[37]

uBlock Origin also supports modifying the response body of a request using the =replace directive. This allows it to effectively alter and deliver the modified response directly to the browser. However, this functionality is currently supported only on Firefox and Firefox-based browsers.[38]

Performance and efficiency

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Technology websites and user reviews for uBlock Origin have regarded the extension as less resource-intensive than extensions that provide similar feature sets such as Adblock Plus.[39][40][41] A benchmark test, conducted in August 2015 with ten blocking extensions, showed uBlock Origin as the most resource-efficient among the extensions tested.[42]

uBlock Origin surveys what style resources are required for an individual web page rather than relying on a universal style sheet. The extension takes a snapshot of the filters the user has enabled, which contributes to accelerated browser start-up speed when compared to retrieving filters from cache every time.[43]

Differential updates

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Starting with version 1.54, uBlock Origin introduced the implementation of differential updates (delta updates), which allows the extension to fetch only changes to filter lists rather than downloading the entire list. This results in lower bandwidth consumption and more frequent updates. This change was part of uBlock Origin's efforts to reduce both requests and bandwidth usage, with the goal of not being ranked among the most bandwidth-intensive projects on jsDelivr, as reflected in public statistics.[44][45]

Limitations in Chromium-based browsers

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According to Raymond Hill, the creator and lead developer of the extension, uBlock Origin works best on Firefox. The main reason is that uBlock Origin (uBO) faces several technical limitations when used on Chromium-based browsers compared to its performance on Firefox, and as a result, users may experience less effective ad blocking, potential exposure to unwanted content, and slower performance when using uBO on Chromium-based browsers.[46]

CNAME Uncloaking

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In November 2019, a uBlock Origin user reported a novel technique used by some sites to bypass third-party tracker blocking. These sites link to URLs that are sub-domains of the page's domain, but those sub-domains resolve to third-party hosts via a CNAME record. Since the initial URL contained a sub-domain of the current page, it was interpreted by browsers as a first-party request and so was allowed by the filtering rules in uBlock Origin (and in similar extensions). The uBlock Origin developer came up with a solution using a DNS API which is exclusive to Firefox 60+.[47] The new feature was implemented in uBlock Origin 1.25, released on February 19, 2020.[48]

Chromium-based browsers lack the ability to uncloak third-party servers disguised as first-party through CNAME records. This limitation reduces the efficiency of blocking third-party trackers, a capability that uBO fully utilizes on Firefox.

Reception

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uBlock Origin is a widely praised content-filtering extension, known for being less memory-intensive than similar tools.[49][50][51][52] Its primary purpose is to give users control over their content-filtering choices, particularly in blocking advertisements and enhancing privacy.[53][54]

The extension has received positive feedback from both users and academic researchers. It is frequently recognized for its effectiveness in blocking ads, improving privacy, and boosting browsing efficiency.[39][40][41] Numerous studies and scientific papers have examined uBlock Origin's impact on web performance, privacy, and user experience. These studies have contributed to a better understanding of the benefits of ad-blocking tools, with uBlock Origin often cited as one of the most comprehensive and efficient solutions. Its widespread use and inclusion in academic research highlight its importance in the broader context of digital privacy and online security.[55]

uBlock Origin is also appreciated for its commitment to remaining a non-profit project.[56] It does not accept paid advertisements and refuses donations, encouraging users to support the maintainers of block lists directly.[57] This commitment to independence helps reinforce its reputation as a privacy-focused tool without commercial interests.

Additionally, it has been praised for its positive environmental impact. By reducing web page load times, it can lead to significant energy savings. Widespread adoption of the tool could help lower energy consumption and mitigate environmental harm.[58]

Supported platforms

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The main version of uBlock Origin is supported on Mozilla Firefox and Chromium-based browsers, although support on the latter is being phased out by major browsers (including Google Chrome and Microsoft Edge) due to its use of a deprecated extension API.[59]

uBlock Origin Lite

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uBlock Origin Lite (uBOL) is a lightweight fork of uBlock Origin designed to be compatible with the current "Manifest V3" (MV3) extension specifications for Chromium-based web browsers.[60] It is therefore the only variant of uBlock Origin officially supported by Chromium-based browsers that have deprecated older extension APIs.[61] In August 2025, uBlock Origin Lite was also released for Safari on iOS, iPadOS, and macOS.[60][62]

Unlike the original version of uBlock Origin, uBOL uses declarative rulesets compiled from existing uBO filter lists, and runs within an MV3 "Service Worker". Due to the architectural changes and limitations of MV3, its filtering capabilities are less granular than the mainline uBO (using a slider-based interface with "Basic", "Optimal", and "Complete" modes), not all of the cosmetic filtering capabilities of uBO are available in uBOL, filters cannot be updated independently of the extension itself, and custom filter lists cannot be added. These architectural changes allow the extension to operate in a more efficient manner than the mainline version of uBO.[63][64][65]

A 2025 quantitative study by researchers at Goethe University Frankfurt found that uBOL's blocking capabilities were on par with (and, in some cases, slightly improved over) the mainline version of uBO, although its cosmetic filters were found to be around 20% less effective in testing.[66]

See also

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Notes

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  1. ↑ uBlock was initially named "μBlock", but it was later renamed to "uBlock" so as to avoid confusion with how the Greek letter μ (Mu/Micro) should be pronounced.[citation needed]

References

[edit]
  1. 1 2 "Contributors to gorhill/uBlock". GitHub. Archived from the original on December 14, 2019. Retrieved December 4, 2019.
  2. ↑ "Changelog for the first versions". GitHub. Archived from the original on December 23, 2019. Retrieved December 4, 2019.
  3. ↑ "Release 1.73.0". August 5, 2026. Retrieved August 6, 2026.
  4. ↑ "Completed translations". Crowdin.com. Archived from the original on October 29, 2019. Retrieved May 16, 2024.
  5. ↑ "uBlock Origin: README.md". uBlock GitHub Repository. December 25, 2022. Archived from the original on January 31, 2022. Retrieved August 23, 2015 – via GitHub. pronounced you-block origin (/ˈjuːˌblɒk/)
  6. ↑ "uBlock Origin Chrome". chrome.google.com. Archived from the original on February 5, 2021. Retrieved April 27, 2025.
  7. ↑ "Search results for Firefox Browser add-ons". Firefox Browser Add-ons. Mozilla Foundation. Retrieved April 27, 2025.
  8. 1 2 "uMatrix". GitHub. Archived from the original on January 31, 2022. Retrieved December 4, 2019.
  9. ↑ "History for icon_128.png - gorhill/httpswitchboard". GitHub. Archived from the original on August 18, 2025. Retrieved December 17, 2024.
  10. ↑ gorhill. "FAQ". httpswitchboard. GitHub. Archived from the original on December 19, 2024. Retrieved December 17, 2024.
  11. ↑ gorhill. "HTTP Switchboard 1.0.0.2 ·". Release. GitHub. Archived from the original on August 19, 2025. Retrieved December 17, 2024.
  12. ↑
  13. ↑ Hill, Raymond (December 9, 2024). "Browser session benchmarker". sessbench. gorhill/github. Archived from the original on August 17, 2025. Retrieved December 17, 2024.
  14. ↑ Brinkmann, Martin (June 24, 2014). "uBlock for Chrome is a resource-friendly adblocker by the HTTP Switchboard author - gHacks Tech News". gHacks. Archived from the original on March 24, 2020. Retrieved December 17, 2024.
  15. ↑ "Home". uMatrix wiki. GitHub. Archived from the original on July 13, 2025. Retrieved December 17, 2024.
  16. ↑ "Adblock Plus is probably the reason Firefox and Chrome are such memory hogs". news.ycombinator.com | Hacker News. Archived from the original on September 14, 2024. Retrieved December 17, 2024.
  17. ↑ Raymond Hill (gorhill). "uMatrix". chromewebstore.google.com - Chrome Web Store. Archived from the original on August 17, 2025. Retrieved December 17, 2024.
  18. ↑ "uMatrix – Extension for Firefox". addons.mozilla.org. Retrieved December 17, 2024.
  19. ↑ Raymond Hill (gorhill) (August 2, 2020). "Request for a stable uMatrix release (for CNAME uncloaking)". Reddit. Archived from the original on May 28, 2023. Retrieved May 4, 2025.
  20. ↑ Brinkmann, Martin (June 24, 2014). "uBlock for Chrome is a resource-friendly adblocker by the HTTP Switchboard author". gHacks Technology News. Ghacks. Archived from the original on February 21, 2025. Retrieved February 22, 2025.
  21. ↑ Hill, Raymond (June 4, 2018). "Changes from HTTP Switchboard". GitHub. Archived from the original on January 31, 2025. Retrieved February 22, 2025.
  22. ↑ Levine, Barry (October 14, 2015). "The Ad Blocker Landscape: What You Need To Know Today". Marketing Land. Archived from the original on February 26, 2021. Retrieved October 17, 2015.
  23. ↑ "The state of ad blocking - September 2015". Sourcepoint and comScore. September 16, 2015. Archived from the original on September 29, 2015. Retrieved October 17, 2015.
  24. ↑ "uBlockAdmin/uBlock". github.com. Retrieved December 4, 2019.
  25. ↑ "An update on uBlock". ublock.org. July 13, 2018. Archived from the original on July 19, 2018. Retrieved December 4, 2019.
  26. ↑ "uBlock Incorporates Acceptable Ads". February 23, 2019. Archived from the original on November 30, 2019. Retrieved December 4, 2019.
  27. ↑ "uBlock 0.9.5.13". GitHub. February 13, 2019. Archived from the original on August 16, 2025. Retrieved June 26, 2020.
  28. ↑ "About Adblock Plus". adblockplus.org. Archived from the original on October 9, 2010. Retrieved December 4, 2019.
  29. ↑ Hill, Raymond (April 3, 2015), "Release 0.9.3.0", gorhill/uBlock, archived from the original on January 24, 2025, retrieved December 8, 2023
  30. ↑ Hill, Raymond. "Please clarify uBlock0 vs. uBlock". Github.com. Archived from the original on January 5, 2022. Retrieved December 4, 2019.
  31. ↑ Hill, Raymond, Update README.md, archived from the original on December 12, 2024, retrieved December 8, 2023
  32. ↑ Hill, Raymond (October 21, 2017). "uBlock Origin is completely unrelated to the web site ublock.org". github.com. Archived from the original on February 9, 2022. Retrieved December 4, 2019.
  33. ↑ "uBlock / README.md". GitHub. Archived from the original on January 31, 2022. Retrieved December 4, 2019.
  34. ↑ "uAssets/filters/badware.txt at master · uBlockOrigin/uAssets". GitHub. Archived from the original on July 23, 2024. Retrieved August 3, 2024.
  35. ↑ "Prevent WebRTC from leaking local IP address". GitHub, gorhill/uBlock. Archived from the original on February 21, 2016. Retrieved May 5, 2023.
  36. ↑ "uBlock wiki". GitHub. Archived from the original on February 15, 2022. Retrieved June 13, 2015.
  37. ↑ "Inline script tag filtering – Overwiew". GitHub, gorhill/uBlock. Archived from the original on February 19, 2020. Retrieved March 20, 2017.
  38. ↑ "Implement network filter option 'replace=' · gorhill/uBlock@7c3e060". GitHub. Archived from the original on May 22, 2025. Retrieved May 20, 2025.
  39. 1 2 "uBlock ad blocker added to Mozilla's extensions site". Jim Lynch, Technology and Other Musings. Archived from the original on April 1, 2016. Retrieved February 17, 2015.
  40. 1 2 Kesari, Varun (October 28, 2017). "Adblock Plus vs uBlock Origin | Which one to Choose In 2017? | RMG". rootmygalaxy.net. Archived from the original on October 28, 2017. Retrieved October 28, 2017.
  41. 1 2 Harper, Christopher (May 2, 2015). "uBlock Origin - Better Than AdBlock Plus?". Make Tech Easier. Archived from the original on February 26, 2020. Retrieved May 27, 2017.
  42. ↑ "10 Ad Blocking Extensions Tested for Best Performance". Raymond Tech Resources. August 26, 2015. Archived from the original on January 5, 2022. Retrieved August 26, 2015.
  43. ↑ "Notes on memory benchmarks, selfies". uBlock GitHub documentation. Archived from the original on February 9, 2022. Retrieved February 17, 2015.
  44. ↑ "Release 1.54.0 · gorhill/uBlock". GitHub. Archived from the original on September 20, 2024. Retrieved October 20, 2024.
  45. ↑ "Usage Statistics". jsDelivr. Archived from the original on October 21, 2024. Retrieved October 20, 2024.
  46. ↑ "uBlock Origin works best on Firefox". GitHub. Archived from the original on September 6, 2024. Retrieved September 3, 2024.
  47. ↑ "uBlock Origin Now Blocks Sneaky First-Party Trackers in Firefox". BleepingComputer. Archived from the original on April 29, 2020. Retrieved February 26, 2020.
  48. ↑ "uBlock Origin 1.25 Now Blocks Cloaked First-Party Scripts, Firefox Only". BleepingComputer. Archived from the original on February 25, 2020. Retrieved February 26, 2020.
  49. ↑ Henry, Alan (January 27, 2015). "uBlock, the Memory-Friendly Ad-Blocker, Is Now Available for Firefox". Archived from the original on January 28, 2015. Retrieved December 4, 2019.
  50. ↑ Brinkmann, Martin (October 10, 2014). "How to add custom filters to Chrome ad-blocking extension μBlock". gHacks Technology News. Retrieved December 4, 2019.
  51. ↑ Schofield, Jack (January 29, 2015). "Are there any trustworthy sources for downloading software?". TheGuardian.com. Archived from the original on January 7, 2022. Retrieved December 4, 2019.
  52. ↑ Whitwam, Ryan (February 12, 2015). "μBlock aims to block ads without draining system resources". ExtremeTech.com. Archived from the original on March 24, 2020. Retrieved December 4, 2019.
  53. ↑ "uBlock". github.com. GitHub. Archived from the original on February 25, 2017. Retrieved December 4, 2019.
  54. ↑ Gardiner, Michael (November 5, 2015). "Adblock Plus vs. Ghostery vs. Ublock Origin: Not All Adblockers Were Created Equal". International Business Times. Archived from the original on July 22, 2017. Retrieved December 4, 2019.
  55. ↑ "Scientific papers". GitHub. Archived from the original on December 26, 2024. Retrieved December 26, 2024.
  56. ↑ "MANIFESTO.md". github.com. Archived from the original on March 11, 2020. Retrieved December 4, 2019.
  57. ↑ "Why don't you accept donations?". GitHub. Archived from the original on February 21, 2020. Retrieved January 20, 2020.
  58. ↑ Pearce, Joshua M. (June 2020). "Energy Conservation with Open Source Ad Blockers". Technologies. 8 (2): 18. doi:10.3390/technologies8020018. ISSN 2227-7080.
  59. ↑ "Firefox stunts on Edge as Microsoft gears up to neuter adblockers: 'uBlock Origin isn't going anywhere'". PC Gamer. August 11, 2026. Retrieved August 13, 2026.
  60. 1 2 "uBlock Origin is about to stop working on Edge. Will you swap browsers, ad blockers, or do nothing?". Windows Central. August 10, 2026. Retrieved August 13, 2026.
  61. ↑ "Chrome Users Beware: Manifest V3 is Deceitful and Threatening". EFF. December 9, 2021. Archived from the original on May 16, 2023. Retrieved April 25, 2024.
  62. ↑ Pot, Justin (August 5, 2025). "The Best Ad Blocker Now Works on Safari Too". Lifehacker. Retrieved August 13, 2026.
  63. ↑ "Ublock Origin Stopped Working | Manifest V3 uBlock Origin". Ghostery. March 1, 2023. Retrieved January 17, 2026.
  64. ↑ "Frequently asked questions (FAQ) – uBOL". GitHub. Archived from the original on November 22, 2023. Retrieved January 17, 2026.
  65. ↑ Amadeo, Ron (November 21, 2023). "Google Chrome will limit ad blockers starting June 2024". Ars Technica. Archived from the original on November 22, 2023. Retrieved November 22, 2023.
  66. ↑ Lukic, Karlo; Papadopoulos, Lazaros (March 2, 2025). "Privacy vs. Profit: The Impact of Google's Manifest Version 3 (MV3) Update on Ad Blocker Effectiveness". arXiv.org. Retrieved August 13, 2026.
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