Verdict
Chrome users should use uBlock Origin Lite as the closest practical MV3-compatible option from the same developer. Firefox remains a practical path for users who specifically need classic uBlock Origin behavior. Old CRX copies of classic uBlock Origin from unofficial sources are not recommended, regardless of browser.
Key Differences
- Classic uBlock Origin uses Manifest V2; uBlock Origin Lite uses Manifest V3. Chrome 138+ disabled MV2 extensions for ordinary users.
- Chrome does not run classic uBlock Origin; uBlock Origin Lite is the available Chrome Web Store option from the same developer.
- uBlock Origin Lite uses a declarative filtering model that differs from classic uBlock Origin's more flexible approach.
- Advanced uBlock Origin features like dynamic rules and some scriptlet injections have more limited equivalents in uBlock Origin Lite.
- Firefox still supports MV2 extensions and may have classic uBlock Origin available, making it a practical option for users who need the original extension behavior.
Side-by-side Comparison
| Option | Best For | MV3 | Cost | Open Source | Setup | Main Trade-off |
|---|---|---|---|---|---|---|
| uBlock Origin (classic) | Firefox users who need full uBlock Origin behavior | No (MV2 only) | Free / Open source | Fully open source | Easy | Not available in modern Chrome for ordinary users |
| uBlock Origin Lite | Chrome users who want the closest option from the same developer | Yes (MV3) | Free / Open source | Fully open source | Easy | Fewer advanced controls than classic uBlock Origin |
| Firefox with classic uBlock Origin | Users who need classic uBlock Origin and are willing to use Firefox | Yes (MV2 still supported) | Free | Fully open source | Moderate | Requires using Firefox instead of Chrome |
| Other Chrome Web Store ad blockers | Chrome users who need ad blocking without specific uBlock features | Yes (MV3) | Free / Paid | Varies | Easy | Different filtering models and feature sets |
| Old CRX copies of classic uBlock Origin | Not recommended for any use case | No | N/A | Unknown | N/A | Risky — unofficial sources can modify extension packages |
Which One Should You Choose
You use Chrome and want the closest MV3-compatible option from the same developer as classic uBlock Origin.
Firefox with classic uBlock Origin
You need specific uBlock Origin features that are not yet available in uBlock Origin Lite and are willing to use Firefox as your primary browser.
Other Chrome Web Store ad blockers
Your workflow does not depend on specific uBlock-specific controls and you need reliable ad blocking in Chrome.
You are considering unofficial downloads of classic uBlock Origin — these are not recommended regardless of browser.
Common Failed Fixes
Trying to: Installing old CRX copies of classic uBlock Origin from mirror sites
Why it does not work: Unofficial CRX files may be outdated, modified, or contain unwanted code. Chrome does not support MV2 extensions, so the CRX file will not install properly in modern Chrome regardless.
Safer alternative: Use uBlock Origin Lite from the Chrome Web Store, or Firefox with classic uBlock Origin.
Trying to: Assuming uBlock Origin Lite behaves identically to classic uBlock Origin in all cases
Why it does not work: uBlock Origin Lite uses a declarative filtering model constrained by MV3. Some advanced dynamic filtering rules and scriptlet injections from classic uBlock Origin are not available or work differently.
Safer alternative: Review uBlock Origin Lite's feature set before migrating, and test filtering behavior on your most-visited sites.
Trying to: Keeping an outdated Chrome build to preserve MV2 support
Why it does not work: Using outdated Chrome versions for MV2 extension support creates security vulnerabilities. Chrome releases security patches that older versions do not receive.
Safer alternative: Use a modern Chrome build with uBlock Origin Lite or consider Firefox as a secondary browser.
Trying to: Installing multiple ad blockers simultaneously in Chrome
Why it does not work: Multiple MV3 content blockers running at the same time can conflict, cause duplicate filtering, or degrade browser performance without improving blocking results.
Safer alternative: Use a single well-maintained ad blocker rather than stacking multiple extensions.
Frequently Asked Questions
Sources
- Chrome Manifest V2 Deprecation TimelineGoogle Chrome DevelopersPrimary source
Supports: Chrome MV2 deprecation schedule and affected extensions
- uBlock Origin Lite — Chrome Web StoreChrome Web StorePrimary source
Supports: Official Chrome Web Store listing for uBlock Origin Lite
- uBlock Origin GitHub RepositoryRaymond HillPrimary source
Supports: Official source for uBlock Origin and uBlock Origin Lite development
- uBlock Origin Lite — Firefox Add-onsMozillaPrimary source
Supports: uBlock Origin Lite availability for Firefox