CSS Designer and Live View: Reconciling Duplicate Rules with Cached Computed Styles

Authoritative Representation

When CSS Designer emits duplicate auto-prefixed rules and Live View diverges from Design view, the stylesheet on disk remains the single source of truth. Duplicates in the panel reflect what was written to the file; Live View shows the browser-engine interpretation after its internal cascade and cache.

Consolidating Duplicate Rules

Dreamweaver CC 2022–2024 has no built-in preference to merge or suppress vendor-prefixed duplicates. The only supported workflow to avoid manual editing is:

1. Disable auto-prefixing in Preferences → CSS Styles → uncheck "Auto-generate vendor prefixes"
2. Generate prefixes externally using a post-processor (Autoprefixer via PostCSS, Gulp, or npm script)
3. Import the clean output back into your project

This shifts prefix management to your build pipeline and ensures deduplication at the source.

Live View Cache Reconciliation

Live View uses an embedded Chromium renderer (CEF) that caches computed styles. Adobe does not expose a documented UI command to force a full computed-style cache invalidation. To reconcile:

1. Save all files (Ctrl/Cmd + S)
2. Switch to Design view
3. Choose View → Refresh Live View (Ctrl+Alt+R / Cmd+Opt+R)
4. If divergence persists, close the document tab and reopen it to reset the CEF instance

Note: Refresh Live View reloads the document but does not guarantee CEF's internal style-cache flush across all frames or shadow DOM.

Release Notes Context

Adobe's Dreamweaver release notes for CC 2022 through 2024 mention Live View performance improvements and CEF upgrades but do not describe a cache-refresh API or CSS Designer consolidation setting. The behavior is consistent across these versions unless a specific hotfix altered caching (none documented).

Verification Steps

• Open Preferences → CSS Styles and confirm the "Auto-generate vendor prefixes" toggle state; toggle off, save a test rule, and inspect the .css file for duplicate selectors.
• In a test page, add a rule that triggers prefixes (e.g., display: grid), open Live View, open DevTools (F12 in Live View), compare the Computed tab with Design view; then close/reopen the document and re-check.
• Run a PostCSS/Autoprefixer build on the same source and diff the output against Dreamweaver's generated CSS to confirm duplicate elimination.

Missing Diagnostic Detail

If the above workflow does not resolve your issue, please specify whether the duplicate rules appear in the on-disk CSS file or only within the CSS Designer panel (which would indicate a panel display issue rather than a file generation issue).