Frequently Asked Questions (FAQ) · uBlockOrigin/uBOL-home Wiki

This FAQ addresses common questions about uBlock Origin (uBO) and uBlock Origin Lite (uBOL), focusing on their differences, limitations, performance, and usage in the context of Chrome's Manifest V3 transition. Key topics include filtering capabilities, update mechanisms, and practical advice for users transitioning to MV3-compliant blockers.

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1. Will uBO Automatically Transition to uBO Lite in the Chrome Web Store?

No. You'll need to manually find an alternative for uBO before Google Chrome disables it permanently. The creator considers uBO Lite "too different" from uBO to be an automatic replacement. Users should evaluate whether uBOL meets their needs based on their browsing habits and configuration preferences.

"See latest Google Chrome announcement regarding the phasing out of MV2 extensions."

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2. If I Install uBOL, Will I See a Difference with uBO?

Possibly, but it depends on:

• The websites you visit
• How you've configured uBO
• Your uBOL settings

Key differences:

• Cosmetic filtering: Not enabled by default in uBOL; you must switch to Complete mode.
• Effectiveness: uBOL may struggle with anti-content-blocker websites or minimize breakage due to limitations in MV3's declarativeNetRequest API.

"In general, uBOL will be less effective at dealing with websites using anti-content blocker because many filters can't be converted into DNR rules."

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3. Is uBOL More Efficient CPU- and Memory-Wise Than uBO?

Performance comparisons require proper benchmarks, but uBOL's fully declarative approach offers advantages:

• Chromium's C++-based DNR implementation vs. Firefox's JavaScript-based one (less optimized).
• uBO's JavaScript filtering engine has historically outperformed some Rust-based engines (though differences are negligible for users).

Addendum: A DebugBear benchmark highlights trade-offs between MV2 and MV3 blockers.

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4. Filtering Capabilities Which Can't Be Ported to MV3

Due to MV3's declarativeNetRequest API limitations, uBOL lacks several uBO features:

• Context-aware filtering: No per-site switches (e.g., no remote fonts/scripting).
• Dynamic filtering: Unable to enforce rules based on response headers or regex patterns.
• Advanced filter options: strict1p, header=, redirect-rule=, and regex-based modifiers are unsupported.
• CNAME-uncloaking: Not supported by any DNR implementation.

"Many very useful regex-based filters used in uBO are not allowed, or are rejected by the DNR API."

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5. When Do Filter Lists Update?

uBOL's "filter lists" are pre-compiled into declarative rulesets during extension updates. Unlike uBO, it:

• Never requests updates from remote servers.
• Relies on the extension's version updates (per webextensions #112).

"Injecting content scripts in MV3 is unreliable because service workers can be suspended at any time."

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6. Is the Limit on Maximum Number of DNR Rules an Issue?

Not currently:

• Guaranteed minimum: 30K static rules (global limit in Chromium: 330K).
• uBOL usage: Default ruleset ~17K (Optimal/Complete modes). Even with all Annoyances and regional rulesets, total stays under 30K.

"Special attention has been given to generate the smallest amount of rules when compiling filter lists."

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7. What Are the Upsides of an MV3-Based Content Blocker?

For Chromium users, uBOL's declarative approach ensures:

• Reliable filtering at browser launch (unlike MV2 blockers).
• No service worker delays: Filters are enforced immediately, even if the service worker is suspended.

"This is not an issue for Firefox MV2-based uBO."

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8. Is uBO Lite a Bad Faith Attempt at Converting uBO to MV3?

No. The creator emphasizes uBOL's purpose is to provide a reliable and efficient MV3 blocker, not a direct uBO replacement. Trade-offs include:

• Limited customization (no filter list imports or custom rules).
• Sacrificed advanced features for compatibility and performance.

"uBO Lite is meant as a reliable Lite version of uBO, suitable for those who used uBO in an install-and-forget manner."

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9. Can I Use Other Content Blockers Along uBO Lite?

Avoid combining blockers (as with uBO):

• Conflicts may occur due to overlapping rules.
• Troubleshooting steps:
  1. Try a different filtering mode.
  2. Disable all other extensions to isolate issues.

"See this tweet for context on uBO + other blockers."

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10. Is the Development of uBO Lite Frozen?

No, but updates will prioritize:

• Maintaining reliability and efficiency.
• Avoiding features that could undermine uBOL's declarative strengths or increase maintenance burden.

"I will be extremely careful to... not add features which may end up undermining the current upsides of uBO Lite."

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Conclusion

uBO Lite is a pragmatic solution for Chromium users transitioning to MV3, offering reliability at the cost of advanced features. While it may not replace uBO for power users, it serves as a lightweight, efficient alternative for those prioritizing seamless filtering. Always test configurations and consider your browsing needs when choosing between blockers. 🛡️