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{"id": 5133099851317248, "name": "CSS update: decoupling of Width and Style properties", "summary": "Chrome 147 aligns with updated [CSS specifications](https://www.w3.org/TR/css-2025/) regarding the behavior of `border-width`, `outline-width`, and `column-rule-width` properties. Previously, if the corresponding `border-style`, `outline-style`, or `column-rule-style` was set to `none` or `hidden`, the computed width of these properties would be forced to `0px`, regardless of the specified value.\n\nWith this change, the computed values of `border-width`, `outline-width`, and `column-rule-width` will always reflect the author-specified values, independent of the `*-style` property. 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"editors": ["javiercon@microsoft.com"], "cc_recipients": ["almaher@microsoft.com", "andruud@chromium.org"], "spec_mentors": ["kbabbitt@microsoft.com"], "creator": "samomekarajr@microsoft.com", "feature_type": "New or changed feature", "feature_type_int": 0, "intent_stage": "None", "intent_stage_int": 0, "active_stage_id": 5073380814094336, "bug_url": "https://issues.chromium.org/issues/393631108", "launch_bug_url": null, "new_crbug_url": "https://bugs.chromium.org/p/chromium/issues/entry?components=Blink>CSS&blocking=393631108&cc=samomekarajr@microsoft.com,kbabbitt@microsoft.com", "screenshot_links": [], "first_enterprise_notification_milestone": 137, "enterprise_impact": 2, "breaking_change": false, "confidential": false, "shipping_year": 2026, "flag_name": null, "finch_name": "DecoupleComputedBorderWidthFromStyle,DecoupleResolvedColumnRuleWidthFromStyleEnabled", "non_finch_justification": null, "ongoing_constraints": null, "rollout_plan": 0, "rollout_plan_displayname": "Will ship enabled for all users", "motivation": "Today, CSS special-cases \u2018border-*-width\u2019, \u2018outline-width\u2019, and \u2018column-rule-width\u2019 so that their computed value becomes \u20180px\u2019 when the corresponding \u2018*-style\u2019 is \u2018none\u2019 or \u2018hidden\u2019, even if the author specified a nonzero width. With Gap Decorations extending \u2018column-rule-*\u2019 properties to support lists/repeaters, applying that special-case becomes ambiguous and difficult to define consistently. Having \u2018*-width\u2019 values independent of \u2018*-style\u2019, provides an intuitive model for these properties and better reflects the author-specified value.", "devtrial_instructions": null, "activation_risks": null, "measurement": null, "availability_expectation": null, "adoption_expectation": null, "adoption_plan": null, "initial_public_proposal_url": "https://github.com/w3c/csswg-drafts/issues/11494", "explainer_links": [], "requires_embedder_support": false, "spec_link": "https://github.com/w3c/csswg-drafts/pull/11913/files", "api_spec": false, "automation_spec": false, "interop_compat_risks": "The interoperability risk is low as both Gecko and Webkit have already implemented these changes.\n\nCompatibility risk is also low. The resolved value for `border-width` via `getComputedStyle()` will remain 0px when `border-style` is set to `none`/ `hidden`, maintaining backward compatibility. For `outline-width` and `column-rule-width`, both computed and resolved values will show the specified values, as these properties are rarely queried and unlikely to impact existing content. To support the claim, we collected UseCounter data measuring how often these values are queried. \n\nThe computed\u2011value counters for these properties are extremely low (<0.0001%). The resolved\u2011value counters for \u2018column-rule-width\u2019 and \u2018outline-width\u2019 show ~2.37% usage, which reflects calls to \u2018getComputedStyle()\u2019 rather than observable rendering usage. Since \u2018getComputedStyle()\u2019 is frequently queried by automated tooling (e.g. scrapers and fingerprinting scripts) that do not depend on property semantics, this usage does not indicate meaningful web\u2011facing reliance. As a result, the compatibility risk remains low.\n", "all_platforms": true, "all_platforms_descr": null, "non_oss_deps": null, "anticipated_spec_changes": null, "security_risks": null, "ergonomics_risks": null, "wpt": true, "wpt_descr": "https://wpt.fyi/results/css/css-backgrounds/animations/border-width-interpolation.html\n\nhttps://wpt.fyi/results/css/CSS2/ui/outline-width-096.xht\n\nhttps://wpt.fyi/results/css/CSS2/borders/border-width-011.xht\n\nhttps://wpt.fyi/results/css/CSS2/borders/border-width-012.xht\n\nhttps://wpt.fyi/results/css/css-ui/parsing/outline-width-computed.html\n\nhttps://wpt.fyi/results/css/css-ui/outline-009.html\n\nhttps://wpt.fyi/results/css/css-ui/animation/outline-width-interpolation.html\n\nhttps://wpt.fyi/results/css/css-multicol/parsing/column-rule-width-computed.html\n\nhttps://wpt.fyi/results/css/css-multicol/parsing/column-rule-computed.html\n\nhttps://wpt.fyi/results/css/css-backgrounds/animations/border-width-interpolation.html", "webview_risks": null, "devrel_emails": ["devrel-chromestatus-all@google.com"], "debuggability": "No extra functionality is needed in Devtools to debug this feature update.", "doc_links": [], "sample_links": [], "prefixed": null, "tags": ["column-rule-width", "border-width", "outline-width"], "tag_review": null, "tag_review_status": "Not applicable", "tag_review_status_int": 4, "security_review_status": "Pending", "security_review_status_int": 1, "privacy_review_status": "Pending", "privacy_review_status_int": 1, "security_continuity_id": null, "security_launch_issue_id": null, "updated_display": null, "resources": {"samples": [], "docs": []}, "comments": null, "ff_views": 1, "safari_views": 1, "web_dev_views": 4, "browsers": {"chrome": {"bug": "https://issues.chromium.org/issues/393631108", "blink_components": ["Blink>CSS"], "devrel": ["devrel-chromestatus-all@google.com"], "owners": ["samomekarajr@microsoft.com", "kbabbitt@microsoft.com"], "origintrial": false, "prefixed": null, "flag": false, "status": {"text": "Proposed", "val": 2, "milestone_str": "Proposed"}, "announced": true, "desktop": 147, "android": 147, "webview": 147, "ios": null}, "ff": {"view": {"url": "https://bugzilla.mozilla.org/show_bug.cgi?id=1998285", "notes": null, "text": "Shipped/Shipping", "val": 1}}, "safari": {"view": {"url": "https://bugs.webkit.org/show_bug.cgi?id=304940", "notes": null, "text": "Shipped/Shipping", "val": 1}}, "webdev": {"view": {"text": "No signals", "val": 4, "url": null, "notes": null}}, "other": {"view": {"text": null, "val": null, "url": null, "notes": null}}}, "standards": {"spec": "https://github.com/w3c/csswg-drafts/pull/11913/files", "maturity": {"text": null, "short_text": "Unknown status", "val": 0}}, "is_released": false, "is_enterprise_feature": false, "experiment_timeline": null, "ai_test_eval_report": null, "ai_test_eval_run_status": null, "ai_test_eval_status_timestamp": null}