What is PixelPilot uiux-performance.instructions.md?

A guide to making web pages load quickly and respond smoothly, using measures such as Core Web Vitals. It explains loading fonts, images, scripts, and other page resources.

Use it to set performance budgets, improve loading behavior, choose image formats, and check page speed on real devices.

It helps identify and reduce slow loading, delayed interaction, and unexpected layout movement that make a site difficult to use.

How dev-lou/PixelPilot configures GitHub Copilot

Reuse

Borrowing it

Nothing to install: this file belongs to dev-lou/PixelPilot. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/dev-lou/PixelPilot/main/vscode/.github/instructions/uiux-performance.instructions.md

Clone the repo

git clone --depth 1 https://github.com/dev-lou/PixelPilot

Made for: GitHub Copilot.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/dev-lou/pixelpilot/uiux-performance/github.svg)](https://agentmods.dev/instructions/dev-lou/pixelpilot/uiux-performance)

Your own site

<a href="https://agentmods.dev/instructions/dev-lou/pixelpilot/uiux-performance"><img src="https://agentmods.dev/badge/instructions/dev-lou/pixelpilot/uiux-performance/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/dev-lou/pixelpilot/uiux-performance"><img src="https://agentmods.dev/badge/instructions/dev-lou/pixelpilot/uiux-performance.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 5,469 This file is loaded in full into every session.

When invoked 5,469 The same file — it is already loaded in full.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.05469	$0.05469
Opus 5.5	$0.02188	$0.02188
Sonnet 5.5	$0.01094	$0.01094
Haiku 4.5	$0.00547	$0.00547

Measured 2mo ago against content hash c3a30e88c7cc, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

PixelPilot uiux-performance.instructions.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

vscode/.github/instructions/uiux-performance.instructions.md · 663 lines

How it starts

The opening of the file, as written. The whole thing — 663 lines — stays where its author put it; the contents beside it link to each section on GitHub.

UI/UX Performance 2026

Core Web Vitals thresholds, font loading, resource hints, image format decisions, Lighthouse CI, bundle budgets. Performance is UX — slow = broken.

CORE WEB VITALS — 2026 Thresholds

Google's ranking signals. Measure all three on real devices, not just desktop.

Metric	Good	Needs Work	Poor	What it measures
LCP (Largest Contentful Paint)	≤ 2.5s	2.5–4.0s	> 4.0s	When main content loads
CLS (Cumulative Layout Shift)	≤ 0.1	0.1–0.25	> 0.25	Visual stability (no jumps)
INP (Interaction to Next Paint)	≤ 200ms	200–500ms	> 500ms	Responsiveness to interaction

INP replaced FID in March 2024. If your docs still say FID, they're outdated.

What Causes Each Metric to Fail

LCP fails when:

Hero image has no fetchpriority="high" or loading="eager"
Render-blocking CSS/JS delays the paint
Server response time (TTFB) > 800ms
Hero is a CSS background-image (browser can't preload it)
Web font blocks text rendering (no font-display: swap)

CLS fails when:

Images have no width/height attributes (browser doesn't reserve space)
Web fonts swap and cause layout reflow
Ads, embeds, or iframes load without reserved dimensions
Dynamic content injected above existing content

INP fails when:

Long JavaScript tasks (> 50ms) block the main thread
Event handlers do heavy synchronous work
Too many DOM nodes (> 1500 is a warning)
React re-renders entire subtrees on every interaction

FONT LOADING STRATEGY

The Performance Stack (apply in this order)

<!-- 1. Preconnect — tells browser to open connection ASAP -->
<link rel="preconnect" href="https://fonts.bunny.net">
<link rel="preconnect" href="https://fonts.bunny.net" crossorigin>

<!-- 2. Preload the most critical font file directly -->
<!-- Find the actual .woff2 URL from the font CSS, then preload it -->
<link rel="preload"
  href="https://fonts.bunny.net/plus-jakarta-sans/files/plus-jakarta-sans-latin-500-normal.woff2"
  as="font" type="font/woff2" crossorigin>

<!-- 3. Load font CSS non-render-blocking (media trick) -->
<link rel="stylesheet"
  href="https://fonts.bunny.net/css?family=plus-jakarta-sans:400,500,600,700&display=swap"
  media="print" onload="this.media='all'">
<noscript>
  <link rel="stylesheet"
    href="https://fonts.bunny.net/css?family=plus-jakarta-sans:400,500,600,700&display=swap">
</noscript>

Read the full file on GitHub · 663 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2mo ago First seen · 663 lines · 5,469 tokens per session scan A c3a30e88c7cc

Subscribe to this mod's changes

PixelPilot uiux-performance.instructions.md is an instructions file published in the GitHub repository dev-lou/PixelPilot (2 stars, last pushed 7mo ago), licensed MIT. It adds 5,469 tokens to every session, about $0.0219 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

CSS and styling Frontend ai-prompts copilot cursor-rules design-system developer-tools

PixelPilot uiux-performance.instructions.md next to 6 instructions from other repositories
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PixelPilot: Instructions file for GitHub Copilot