speedlify2

Lighthouse lab metrics and Chrome UX Report field data for a list of sites, recorded on every run and compared over time.

Measurement runs · Embed a score · Field data from the Chrome UX Report ·

tc39.es

https://tc39.es/

78 96 100 82 ✓CWV 1AXE

Data from Aug 21, 2026, 8:44 AM UTC — 10h old.

Built Awesome · 1 measurement · since Aug 21, 2026 · last attempt 10h

Stack

Detected on the same page load as the accessibility pass — the generator from <meta name="generator"> or the shape of the page, the host from response headers.

GitHub Pages Hosted by GitHub Pages

Core Web Vitals field data, url-level

Real Chrome users, 28-day window (2026-07-23 → 2026-08-19). This is what Google measures you on.

LCP 1.53 s good
INP — no data
CLS 0 good

Scores

78
Performance
no change
96
Accessibility
no change
100
Best Practices
no change
82
SEO
no change

Lab metrics Lighthouse, mobile

Metric Current Previous Change Best Worst Trend
LCP Largest Contentful Paint 2.46 s — — 2.46 s 2.46 s
CLS Cumulative Layout Shift 0.330 — — 0.330 0.330
TBT Total Blocking Time 0 ms — — 0 ms 0 ms
FCP First Contentful Paint 2.46 s — — 2.46 s 2.46 s
Speed Index 2.46 s — — 2.46 s 2.46 s
TTFB Time to First Byte 609 ms — — 609 ms 609 ms

What LCP is made of

A flat LCP number tells you something regressed. The subparts tell you whether it was the server, resource discovery, the download, or rendering.

element render delay 94 ms
time to first byte 10 ms

Field data Chrome UX Report, url-level

Real Chrome users, 28-day trailing window (2026-07-23 → 2026-08-19). This is what Google measures you on.

Metric p75 Rating Distribution (good / needs work / poor)
LCP CWV 1.53 s good 89.9% good
CLS CWV 0 good 97% good
FCP 1.47 s good 81.5% good

Lab vs field

Lab LCP 2.46 s · field p75 1.53 s · real users are 0.62× faster than the lab.

Field history 25 weeks

Weekly p75 from the CrUX History API, backfilled in a single request.

Week ending LCPINPCLSFCPTTFB
2026-08-15 1.53 s — 0 1.53 s —
2026-08-08 — — 0 1.69 s —
2026-08-01 1.70 s — 0 1.71 s 850 ms
2026-07-25 1.57 s — 0 1.57 s —
2026-07-18 1.56 s — 0 1.56 s —
2026-07-11 1.33 s — 0 1.30 s 773 ms
2026-07-04 1.33 s — 0 1.32 s 870 ms
2026-06-27 1.33 s — 0 1.32 s 826 ms
2026-06-20 1.40 s — 0 1.40 s 770 ms
2026-06-13 1.46 s — 0 1.46 s 883 ms
2026-06-06 1.43 s — 0 1.44 s 855 ms
2026-05-30 1.40 s — 0 1.43 s 730 ms

Page weight

Metric Current Previous Change Best Worst Trend
Page Weight 99.6 kB — — 99.6 kB 99.6 kB
Requests 12 — — 12 12
Third-party Weight 68.0 kB — — 68.0 kB 68.0 kB
Third-party CPU 0 ms — — 0 ms 0 ms
Unused JS 0 B — — 0 B 0 B
Unused CSS 0 B — — 0 B 0 B

By resource type

font 65.9 kB · 2 req
image 15.7 kB · 4 req
document 8.5 kB · 1 req
stylesheet 7.0 kB · 3 req
script 855 B · 1 req
third party 68.0 kB · 3 req

Third parties 1 entities

68.0 kB transferred, 0 ms of main thread time. This is the number most likely to regress without anyone on your team shipping anything.

Google Fonts 68.0 kB · 0 ms CPU

Page health

Metric Current Previous Change Best Worst Trend
Main Thread Work 275 ms — — 275 ms 275 ms
Long Tasks 0 — — 0 0
DOM Elements 357 — — 357 357
Axe Violations Violating nodes from a full axe run — stricter than Lighthouse's subset 1 — — 1 1
A11y Failures 1 — — 1 1
A11y Failing Nodes 1 — — 1 1

Main thread work

style layout 121 ms
other 102 ms
paint composite render 27 ms
parse HTML 12 ms
script evaluation 12 ms
script parse compile 1 ms

Axe violations axe-core 4.13.0, full rule set

1 violating node across 1 rule, 775 passing. This is a standalone axe run, stricter than the subset Lighthouse folds into its score above — and it is the second tiebreaker in the ranking.

  • serious link-name — Links must have discernible text 1 node

Accessibility failures 1 of 25 audits

Tracked as a count, not just the score — the weighted score is coarse enough that you can ship a broken component and barely move it.

  • link-name — Links do not have a discernible name 1 node

Hygiene

Changes rarely — which is exactly why a change is worth noticing.

HTTPS HSTS CSP Clickjacking protection Origin isolation Trusted Types bfcache h2

Measurement log

Every stored run for this URL, newest first. Failures are kept as records — "this site was down on Tuesday" is data too.

When PerfLCPCLSTBTWeight RunsSpreadBenchTook
Aug 21, 2026, 8:44 AM UTC 78 2.46 s 0.330 0 ms 99.6 kB 3/3 ±13 3,332 21.6s

Embed this score

Live below, then the markup that produces it. Drop that on any page to show tc39.es's scores, updated whenever this instance re-measures — more about the component. Don’t forget to bundle the speedlify-score.js component code into your site! 

<speedlify-score speedlify-url="https://zachleat.github.io/speedlify2/" url="https://tc39.es/"></speedlify-score>