Blocking Model

Very Good AdBlock uses a balanced, performance-conscious Manifest V3 architecture:

• Static declarativeNetRequest rules for known network ad domains and URL patterns (~14k hosts plus curated seeds).
• Redirect rules that neuter ad-SDK loaders (gpt.js, adsbygoogle.js) to inert web-accessible stubs instead of hard-blocking them, so pages that await the SDK keep working.
• Dynamic declarativeNetRequest rules for user site overrides; disabling protection installs a single global allow rule that bypasses all blocking.
• Content scripts for cosmetic filtering, YouTube skip automation, and Twitch video-ad marker detection.
• Chrome storage for settings, stats, and cross-install sync.

Static Rules

Static rules are generated at build time from pinned filter sources and curated seeds. They are shipped with the extension and loaded by Chrome through the MV3 ruleset manifest.

Dynamic Rules

Dynamic rules are derived from settings:

• Allowed sites receive allow rules.
• Manually blocked sites receive block rules.
• Rules are bounded to the configured dynamic ID range.

Filter Refresh

MV3 static rules can only change with an extension update, so a daily chrome.alarms job fetches the maintained host list and loads any hosts newer than the shipped ruleset as dynamic rules in a separate reserved ID range. The fetch is bounded, deduped against the shipped set, and non-fatal on failure — the shipped static and dynamic rules stay active regardless.

Content Scripts

Content scripts handle the placements network rules cannot reach:

• Cosmetic filtering hides first-party ad placements (YouTube feed/masthead/display ads, Twitch ad affordances) via a stylesheet injected at document_start so ads never flash in. X promoted tweets are pruned at the source by a MAIN-world script that strips promotedMetadata entries from X's GraphQL responses (uBlock's approach), with a DOM label check as fallback.
• YouTube video ads are pruned at the source by a MAIN-world script that strips adPlacements/adSlots/playerAds from player responses (inline and /youtubei/v1/player), so the real video plays with no pre/mid-roll; skip-button clicks and fast-forward remain as a safety net.
• Pop-up/pop-under defusing: a MAIN-world script wraps window.open and blocks the abusive pattern (cross-origin opens from clicking non-interactive areas, gesture-less opens, floods) while allowing legit pop-ups (OAuth, share); blocked calls get a decoy window so the site doesn't retry.
• Dismissal of YouTube's anti-adblock enforcement popup, restoring scroll and playback.
• Twitch video-ad markers used to estimate saved time.
• Throttled mutation scans that tag hidden placements and catch late-loading video controls and markers.

The goal is to remove interruptions immediately without brittle page-breaking media hacks. Cosmetic hiding is site-specific, ships with global and per-site kill switches, and never touches the player region or real content. See Cosmetic Filtering.