How is the readiness score calculated?

It is priority-weighted, not a flat percentage of items ticked. Each check carries a weight by priority — critical ×10, high ×5, medium ×2, low ×1 — and the score is your earned weight divided by the total available weight, rounded to a whole number out of 100. Passing a critical item like LCP or the viewport meta tag therefore raises the score far more than a low-priority nice-to-have.

What do the score bands mean?

The overall ring and each category bar are banded the same way: 90 or above is "Mobile-ready" (green), 50 to 89 is "Needs work" (amber), and below 50 is "At risk" (red). The per-category bars use each category's own weighted score so you can see exactly where you are losing points.

Does this tool measure my live website?

No. It is a manual audit checklist — you tick the practices you have actually shipped and it scores them. It does not crawl a URL or run Lighthouse. Verify each item with your own tools (DevTools, PageSpeed Insights, the CrUX field-data panel) and tick it once it passes; the tool then weights and totals your answers.

How do I save or share my progress?

Your checked items are encoded directly into the page URL, so copying the link (via the Share button) captures your exact state — no login or local storage involved. You can also export everything as a Markdown checklist (mobile-perf-checklist.md) containing the score, a per-category table, checkbox lines and the Core Web Vitals thresholds, ready to paste into a PR or ticket.

Which Core Web Vitals are referenced?

The reference panel covers the current three: LCP (good ≤ 2.5s), INP (good ≤ 200ms, which replaced FID in 2024) and CLS (good ≤ 0.1), each with its good / needs-improvement / poor thresholds. These are an informational reference; only real field data (CrUX or RUM) confirms your actual numbers.

What does the "fix these first" list show?

It lists your unchecked items sorted by priority — criticals first, then high, medium and low — so the top of the list is always the highest-impact work remaining. The panel shows the top five, and the Markdown export includes them with the specific "how" guidance for each.

Mobile Performance Checker

Audit your site against a weighted mobile-performance checklist — Core Web Vitals, viewport, assets and UX — and get a shareable readiness score.

About this ToolHow it works, benefits & use cases

Audit your site against an opinionated, priority-weighted mobile-performance checklist and watch a 0–100 readiness score react as you tick what you ship. The tool lists 16 checks across four categories — Core Web Vitals, viewport & responsiveness, network & assets, and mobile UX — each tagged Critical, High, Medium or Low, with an expandable "Why & how" note. The score is weighted, not a simple tick-percentage: each item contributes by priority (critical ×10, high ×5, medium ×2, low ×1), so passing the heavy hitters like LCP, INP, the viewport meta tag and image optimization moves the needle far more than nice-to-haves. You get an overall ring (Mobile-ready ≥90, Needs work ≥50, At risk below), per-category bars, a "fix these first" list of your top unchecked items sorted by priority, and a Core Web Vitals threshold reference for LCP, INP and CLS. Check-all and reset buttons let you start clean. Your progress is encoded in the URL so you can share the exact state with your team, and you can export the whole audit as a Markdown checklist to drop into a pull request.

How to Use

1Work through the four category sections and tick every check your site already passes.
2Expand "Why & how" on any item to see why it matters for mobile and how to verify it.
3Watch the weighted readiness ring, per-category bars and band label (Mobile-ready / Needs work / At risk) update live.
4Use the "fix these first" list to tackle your highest-priority unchecked items, and the Core Web Vitals panel as a threshold reference.
5Share the URL to hand your exact progress to a teammate, or export the Markdown checklist for a PR or ticket.

Key Benefits

Priority-weighted score (critical ×10, high ×5, medium ×2, low ×1) — not a flat tick-percentage
16 curated checks across Core Web Vitals, viewport, network/assets and mobile UX
Per-item "Why & how" notes explaining the ranking impact and the fix
Per-category breakdown bars plus an overall readiness ring and band
"Fix these first" list that surfaces your top unchecked items by priority
Shareable URL state — your ticks are encoded in the link, no account or storage needed
Markdown export with score, category table, checkboxes and a Core Web Vitals reference

Common Use Cases

Running a pre-launch mobile readiness pass and tracking it as a weighted score
Prioritising mobile work by fixing the highest-weight unchecked items first
Sharing a snapshot of audit progress with a teammate via the URL
Attaching a Markdown checklist to a pull request or performance ticket
Using the LCP / INP / CLS reference panel as a quick Core Web Vitals cheat sheet

Readiness score

At risk

0/100

0 of 17 checks done · weighted by priority (critical ×10, high ×5, medium ×2, low ×1)

By category

Core Web Vitals0/4 · 0

Viewport & responsiveness0/4 · 0

Network & assets0/5 · 0

Mobile UX0/4 · 0

Fix these first

CriticalLCP under 2.5s on mobile
CriticalINP under 200ms
CriticalResponsive viewport meta tag
CriticalOptimized, modern-format images
HighCLS under 0.1

Core Web Vitals thresholds

LCP Largest Contentful Paint

Loading — time to render the largest visible element.

≤ 2.5s≤ 4s> 4s

INP Interaction to Next Paint

Responsiveness — latency of the worst real interaction.

≤ 200ms≤ 500ms> 500ms

CLS Cumulative Layout Shift

Visual stability — how much the layout unexpectedly shifts.

≤ 0.1≤ 0.25> 0.25

Export

Markdown checklist with your progress

# Mobile Performance Checklist

**Readiness score: 0/100** (poor) — 0/17 items checked

| Category | Score | Items |
| --- | --- | --- |
| Core Web Vitals | 0/100 | 0/4 |
| Viewport & responsiveness | 0/100 | 0/4 |
| Network & assets | 0/100 | 0/5 |
| Mobile UX | 0/100 | 0/4 |

## Core Web Vitals

- [ ] **LCP under 2.5s on mobile** _(critical)_
- [ ] **INP under 200ms** _(critical)_
- [ ] **CLS under 0.1** _(high)_
- [ ] **Measure real field data (CrUX/RUM)** _(medium)_

## Viewport & responsiveness

- [ ] **Responsive viewport meta tag** _(critical)_
- [ ] **No horizontal scrolling** _(high)_
- [ ] **Base font size of at least 16px** _(medium)_
- [ ] **Tap targets at least 44×44px** _(high)_

## Network & assets

- [ ] **Optimized, modern-format images** _(critical)_
- [ ] **Text compression (Brotli/Gzip)** _(high)_
- [ ] **Lazy-load below-the-fold media** _(medium)_
- [ ] **font-display: swap for web fonts** _(medium)_
- [ ] **Minimize & split JavaScript** _(high)_

## Mobile UX

- [ ] **No intrusive interstitials** _(high)_
- [ ] **Touch-friendly interactions (no hover-only)** _(medium)_
- [ ] **Fast Time to Interactive** _(medium)_
- [ ] **Parity for mobile-first indexing** _(low)_

## Fix these first

- **LCP under 2.5s on mobile** _(critical)_ — Preload the LCP image/font, serve it in WebP/AVIF, avoid lazy-loading the hero, and keep render-blocking CSS/JS off the critical path.
- **INP under 200ms** _(critical)_ — Break up long tasks, yield to the main thread, debounce expensive handlers, and avoid hydrating large client components eagerly.
- **Responsive viewport meta tag** _(critical)_ — Add the viewport meta to <head>. Do not disable zoom (no maximum-scale=1 / user-scalable=no) — it harms accessibility.
- **Optimized, modern-format images** _(critical)_ — Serve WebP/AVIF, generate responsive srcset/sizes, compress to ~80% quality, and serve correctly-sized images per breakpoint.
- **CLS under 0.1** _(high)_ — Set width/height (or aspect-ratio) on media, reserve space for ads/embeds, and never inject content above existing content after load.

## Core Web Vitals thresholds

| Metric | Good | Needs improvement | Poor |
| --- | --- | --- | --- |
| LCP | ≤ 2.5s | ≤ 4s | > 4s |
| INP | ≤ 200ms | ≤ 500ms | > 500ms |
| CLS | ≤ 0.1 | ≤ 0.25 | > 0.25 |

Core Web Vitals

The field metrics Google ranks on — LCP, INP and CLS.

Critical

High

Medium

Viewport & responsiveness

Layout that fits the small screen and is comfortable to read and tap.

Critical

High

Medium

High

Network & assets

Ship fewer, smaller, smarter bytes over slow mobile connections.

Critical

High

Medium

High

Mobile UX

Interaction quality and the experience signals Google penalises.

High

Medium

Low

Why mobile performance matters

Google uses mobile-first indexing — it crawls and ranks the mobile version of your site, so anything slow, cramped or hidden on a phone hurts you everywhere. The audit above is weighted: critical fixes (LCP, INP, viewport meta, image optimization) move the needle far more than nice-to-haves.

Core Web Vitals are the field metrics that feed ranking. LCP tracks how fast the largest element paints (good ≤ 2.5s), INP tracks interaction responsiveness (good ≤ 200ms) and CLS tracks visual stability (good ≤ 0.1). Lab tools estimate them; only real field data (CrUX/RUM) confirms them. Tick what you ship, share the URL with your team, and export the Markdown for your PR.

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Mobile Performance Checker

How to Use

Key Benefits

Common Use Cases

Readiness score

By category

Fix these first

Core Web Vitals thresholds

Core Web Vitals

Viewport & responsiveness

Network & assets

Mobile UX

Why mobile performance matters

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Frequently Asked Questions - Mobile Performance Checker