3
Urgent
Performance
Verified by measurement
TBT 1,690ms on MLB
Lab TBT on /en-us/sports/mlb is 1,690ms, blocking main thread interactivity and causing unresponsive taps during load.
scroll ↕ — this is the live page
⚠ TBT 1,690ms on MLBThe page's Total Blocking Time is 1,690ms, far above the 200ms 'good' threshold. This means the main thread is blocked by long-running scripts, so …
Reduce blocking timeImprove interactivityOptimize scripts
Performance
MLB Scores & News
Live scores, schedules, and breaking news for Major League Baseball.
$0.00
ReadyGet Started✓ Instant responsePage is interactive in under 200ms; taps and scrolls respond immediately.
FixOptimize and defer non-critical JavaScript to reduce main-thread blocking. Break up long tasks, use code splitting, and prioritize critical rendering path. This will bring TBT down to under 200ms, making the page feel instant and responsive.
Evidence
Observed on the live site Verified by measurement
✓ Flagged independently by 1 of 7 analysts
- Lighthouse (mobile emulation, single synthetic run via DataForSEO): Total Blocking Time 1,690 ms against a ‘good’ threshold of 200ms. Lab data, not real-user field data — confirms the defect class, not the field percentile.
Business case
If this change wins
0 – 0
orders per 1,000 visitors
Medium
Effort — 2-5 days
Not A/B testable
At typical traffic
Detecting this needs about 124,891 visitors per variant. Ship it as a sequenced change and log the date instead.
Prioritisation
PXL score: 5 / 10
Assessed from the live page
| Question | Answer | Points |
|---|---|---|
| Is the change above the fold? | Yes | 1 |
| Is the change noticeable in under 5 seconds? | Yes | 2 |
| Does it add or remove an element? | Yes | 1 |
| Does it run on a high-traffic page? | No | 0 |
| Verified by direct technical measurement? | Yes | 1 |
Criteria that need your data
4 of these could not be answered from the live page. Session recordings, survey or support themes, and analytics access would raise the confidence of this ranking — they do not indicate a weaker finding.
| Question | Answer | Points |
|---|---|---|
| Discovered via user testing? | No | 0 |
| Discovered via qualitative feedback (survey, support)? | No | 0 |
| Supported by heatmaps or session recordings? | No | 0 |
| Found via digital analytics or real-user field data? | No | 0 |
Implementation
Hand this to your developer
- Surface
- Performance — PERFORMANCE
- Problem
- Lab TBT on /en-us/sports/mlb is 1,690ms, blocking main thread interactivity and causing unresponsive taps during load.
- Current state
- notes: Total Blocking Time 1,690 ms (lab, mobile on /en-us/sports/mlb)
- Change
- notes: Total Blocking Time ≤ 200ms (good)
- Acceptance criteria
- GIVEN a first-time visitor on the affected page
WHEN the change is live
THEN Total Blocking Time ≤ 200ms (good), with no regression at 375px and 1280px widths. - Tracking
- event: cro_tbt_1690ms_on_mlb on interaction with the changed element; verify it fires in BOTH variants before opening traffic.
- Success metric
- conversion rate on the affected step
- QA checklist
- Chrome / Safari / Firefox · 375px + 1280px · keyboard reachable · screen-reader name present · no CLS introduced
- Effort
- Medium — 2-5 days
- Test plan
- 124,891 visitors per variant (95% significance, 80% power); 56 days.
- Rollback
- Feature-flag the change; revert the flag if the primary metric drops for 3 consecutive days.