uBlock Origin vs uBlock Origin Lite after MV3: what you actually lose
The short answer
uBlock Origin Lite covers the common cases with static rules and is lighter, but it drops dynamic filtering, per-site element picking at runtime, and some advanced lists. For most people Lite is fine; power users who rely on dynamic rules should keep the classic build where it's still available.
What changed under MV3?
MV3 replaces the blocking webRequest API with declarativeNetRequest — static, pre-declared rules the browser applies. That's the core reason Lite behaves differently.
What do you lose with Lite?
Dynamic filtering, on-the-fly rule changes, and some large community lists that exceed the rule budget. Element-picker cosmetic filtering still works, but the network side is now rule-limited.
| Capability | uBO (classic) | uBO Lite |
|---|---|---|
| Dynamic filtering | Yes | No |
| Static list blocking | Yes | Yes (rule-capped) |
| Idle memory (our test) | ~90 MB | ~40 MB |
Which should you install?
Lite for lower overhead and set-and-forget blocking; classic where your browser still allows it and you tune rules per site.
Methodology. Method: same 15-site set, cold profiles, memory sampled after 5 min idle. Collected 2026-05-30.