NovaBlock vs uBlock Origin Lite: closer than we expected

First, an important distinction that most comparisons get wrong.

This is uBlock Origin Lite, not uBlock Origin. uBlock Origin proper is a Manifest V2 extension, and current Chromium has removed Manifest V2 support entirely — it will not load at any speed, in any mode. uBlock Origin Lite is the same project's Manifest V3 build and the only version that runs in a modern Chrome. We tested it at its Complete filtering mode with seventeen filter lists enabled: its strongest configuration.

uBlock Origin Lite used 16.85 MB of page memory. We used 11.98 MB. A browser running no extension uses 10.26 MB — so uBO Lite's overhead is roughly 6.6 MB against our 1.7 MB, nearly four times as much.

For a single tab that's academic. Across thirty tabs it isn't.

We're faster where advertising is heaviest. Tom's Hardware — twenty-eight third-party servers unprotected — takes 1021 ms with NovaBlock and 1227 ms with uBO Lite. GitHub, 563 ms to 601 ms. Marca and Wikipedia are dead heats, within 2 ms.

uBlock Origin Lite wins the Guardian, 398 ms to 465 ms, and takes the pooled median across all page loads. We're publishing both numbers rather than the one that suits us.

uBO Lite blocked 241 requests to our 108. But across the same five sites it still contacted 32 third-party servers where we contacted 28.

That's the counting effect described in the footnote below: blocking a tracking company at the domain level prevents far more requests than it records. Both products end up letting through a similar, small number of companies — uBO Lite just documents its work more thoroughly.

On bandwidth we're marginally ahead, 26.3 MB against 26.8, and on tracking scripts prevented from executing, six against five.

This is the closest matchup of the four we ran. uBlock Origin Lite is an excellent, mature product with a far larger filter corpus than ours, and it takes the pooled speed number. We take memory decisively, the heavy pages, and the servers-reached count. If you want the lightest-footprint blocker, that's us. If you want the largest filter corpus available in Manifest V3, that's uBO Lite.

* Why “requests blocked” can be misleading. This number measures blocking style as much as effectiveness. NovaBlock blocks tracking companies at the domain level — the script never loads, so the twenty requests it would have made never happen, and are never counted as blocked. Blockers that let the script run and then kill each beacon it fires score twenty for the same outcome. On Marca, Ghostery blocked 68 requests to NovaBlock's 9 while still contacting more third-party servers (16 against 13). That's why we also report third-party servers reached, which this effect doesn't distort. The gap isn't purely cosmetic — Ghostery genuinely transfers less data overall — but the raw count overstates it substantially.

† Why our tracker score may flatter us. We check whether the JavaScript object each tracker installs is present on the page after loading. Some blockers replace a tracker with a harmless local stand-in rather than blocking it outright; the stand-in defines the same object, so our test records it as “ran” even though no data left the browser. On this measure, their better technique scores worse. We report the figure because we measured it, and the caveat because it's true.