Servo is falling behind the web. It completes ~22 features/year at production quality, while the Baseline “Widely Available” set grows at ~52 features/year. At this pace, Servo plateaus around 80% by ~2037 and never catches up. Full velocity parity requires ~44 FTE (€8.8M/yr, €26.3M over 3yr). BWA features vary widely in real-world usage — a phased approach that prioritizes high-usage features first could reduce the initial headcount and cost by up to 40% while building toward full parity. The highest-leverage actions are unstalling 141 blocked features and fixing 51 regressions (features that lost >5 percentage points). This is a work-in-progress analysis focusing on one aspect of web engine development — feature-level readiness — and is not exhaustive. It is designed to orient thinking about cost and timelines. The central question: what would it cost in engineering investment alone to bring Servo to velocity parity within 3 years, excluding non-engineering and operational costs?
| FTE | Compl/yr | vs All BWA (52/yr) | vs <1% (49/yr) | vs <5% (47/yr) | €/yr | 3yr |
|---|---|---|---|---|---|---|
| 13 (now) | ~22 | ✗ | ✗ | ✗ | €2.6M | €7.8M |
| 25 | ~35 | ✗ | ✗ | ✗ | €5.0M | €15.0M |
| 38 | ~47 | ✗ | ≈ | ✓ | €7.6M | €22.7M |
| 41 | ~49 | ✗ | ✓ | ✓ | €8.2M | €24.5M |
| 44 | ~52 | ✓ parity | ✓ | ✓ | €8.8M | €26.3M |
| 55 | ~60 | ✓ | ✓ | ✓ | €11.0M | €32.9M |
All BWA = 593 features (~52/yr). <1% = drop 35 features below 1% usage (~49/yr). <5% = drop 56 features (~47/yr). Completions/yr = 22 × (FTE/13)0.7. Cost = FTE × €200k (€150k base × 1.33× specialization). Brooks's Law scaling exponent 0.7.
Of 593 BWA features, 439 have WPT test coverage. 154 lack WPT mapping: 78 JS built-ins (SpiderMonkey/test262), 23 semantic HTML elements, 53 other (WebGL extensions, DOM, CSS, etc.). The 78 JS built-ins and 23 semantic HTML elements (~66% of unmeasured) are supported via SpiderMonkey and the HTML parser respectively; the remaining 53 have unknown status. WPT pass rate doubled from 30% to 62% over 2.5 years.
| Year | New BWA | Cumulative | Source |
|---|---|---|---|
| 2026 | +61 | 654 | Known pipeline |
| 2027 | +42 | 696 | Known pipeline |
| 2028 | +27 | 723 | Known pipeline |
| 2029+ | ~52/yr | ~775+ | Projected avg |
| Full BWA | Drop <1% | Drop <5% | |
|---|---|---|---|
| Target features | 593 | 558 (−35) | 537 (−56) |
| BWA growth rate | ~52/yr | ~49/yr | ~47/yr |
| Parity FTE | ~44 | ~41 | ~38 |
| Cost/yr | €8.8M | €8.2M | €7.6M |
| 3yr total | €26.3M | €24.5M | €22.7M |
| 3yr savings | — | €1.8M | €3.6M |
Readiness measured against Baseline “Widely Available” (BWA) web features — supported 30+ months across all major browsers. Feature scores from Web Platform Tests (WPT) via WPT Feature Manifest mapping. 439 of 593 BWA features are measurable; 154 lack WPT mapping (78 JS built-ins tested by test262 not WPT, 23 semantic HTML elements, 53 other with unknown status). FTE-equivalent from per-author commit frequency (1 FTE ≈ 22 commits/month, capped at 1.0 per person; 115 authors sum to ~13 FTE). BWA growth rate of ~52/year is the 2023–2025 average, normalized to exclude the 2022 interop spike. Known pipeline: 130 features graduating by 2028. Velocity parity = Servo’s annual feature completion rate ≥ BWA annual growth rate. Completions/yr = 22 × (FTE/13)0.7 (sublinear Brooks’s Law scaling). Stalled = zero or negative velocity over the full observation period (2023-Q3 to 2026-Q1). Regressions = features that lost >5 percentage points. Cost at €200k/yr per FTE: €150k European senior SWE median total cost × 1.33× premium for browser-engine specialization (small talent pool, Rust/rendering/layout) and multi-disciplinary practice (software development + W3C/WHATWG standards participation + open-source community management). Calibrated against NLnet (€117k, up to €65/hr), Sovereign Tech Fund (€79–101k, TVöD-Bund + employer costs), Mozilla Germany (€145–164k), and Servo grant rates (€248k US contractor). Excludes other opex, infrastructure, management overhead, and inflation. Usage-prioritized scenarios: at <1% threshold, 35 features deprioritized (target 558, growth ~49/yr); at <5%, 56 features deprioritized (target 537, growth ~47/yr). Data: wpt.fyi, web-features, Servo git history. Full interactive dashboard: dashboard.html.
Thanks to the people who’ve reviewed the methodology and approach so far. NOTE: AI was used in the making of this draft report. For suggestions for improvement or spotting of inaccuracies, contact dietrich@webtransitions.org.