Borrowing it
Nothing to install: this file belongs to mrhinkle/VibeCoding-a-Website. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/mrhinkle/VibeCoding-a-Website/main/.claude/skills/performance-optimizer/SKILL.mdgit clone --depth 1 https://github.com/mrhinkle/VibeCoding-a-WebsiteWrote 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.
[](https://agentmods.dev/skills/mrhinkle/vibecoding-a-website/performance-optimizer)<a href="https://agentmods.dev/skills/mrhinkle/vibecoding-a-website/performance-optimizer"><img src="https://agentmods.dev/badge/skills/mrhinkle/vibecoding-a-website/performance-optimizer/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.
<a href="https://agentmods.dev/skills/mrhinkle/vibecoding-a-website/performance-optimizer"><img src="https://agentmods.dev/badge/skills/mrhinkle/vibecoding-a-website/performance-optimizer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00000 | $0.01751 |
| Opus 5.5 | $0.00000 | $0.00700 |
| Sonnet 5.5 | $0.00000 | $0.00350 |
| Haiku 4.5 | $0.00000 | $0.00175 |
Grade A, and why
performance-optimizer 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.
How it starts
The opening of the file, as written. The whole thing — 204 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Performance Optimizer Skill
Overview
This skill audits and fixes page load performance issues on websites. It analyzes images, CSS, JavaScript, fonts, and assets, then generates a before/after performance report with specific optimization recommendations and implementation steps.
Why Performance Matters
- User Experience: Pages that load in under 3 seconds have 40% higher conversion rates than those taking 6+ seconds
- SEO Rankings: Google uses Core Web Vitals as a ranking factor; slow sites rank lower
- Mobile Performance: 53% of users abandon sites that take over 3 seconds to load on mobile
- Cost Savings: Optimized sites consume less bandwidth and server resources
- Business Impact: Every 100ms of latency costs Amazon 1% in sales
Key Optimization Areas
1. Image Optimization
Why it matters: Images typically represent 50-80% of page weight. Optimization directly impacts load time.
Checks performed:
- Image dimensions: Ensures images aren't larger than displayed size
- Compression ratio: Recommends lossy compression for photos, lossless for graphics
- WebP conversion: Identifies images that should use modern WebP format (25-35% smaller)
- Responsive images: Detects missing srcset for different screen sizes
- Lazy loading: Identifies above-the-fold images loading eagerly vs below-the-fold images
- Format selection: PNG for graphics, JPEG for photos, SVG for icons, WebP for all
Deliverables:
- List of images requiring optimization
- Compression commands (ImageMagick, cwebp)
- HTML code samples for srcset implementation
- Lazy-loading implementation guidance
2. CSS Optimization
Why it matters: Render-blocking CSS prevents the page from painting. Unoptimized CSS increases file size and parse time.
Checks performed:
- Minification: Removes whitespace, comments, unnecessary characters
- Critical CSS: Identifies styles needed for above-the-fold content
- Unused CSS: Detects unused selectors (especially from frameworks like Bootstrap)
- Media query optimization: Ensures mobile-specific CSS isn't loaded on desktop
- CSS file splitting: Suggests code splitting for large stylesheets
- Animation efficiency: Recommends transform/opacity over layout-triggering properties
What ships with it
2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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 · 204 lines · 0 tokens per session scan A 5c1ba3cb16a1
performance-optimizer is a skill published in the GitHub repository mrhinkle/VibeCoding-a-Website (17 stars, last pushed 6mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 1,751 tokens. 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 2026-08-30.
performance-optimizer compared with skills from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| performance-optimizermrhinkle/VibeCoding-a-Website | Skill | 17 | 6mo ago | MIT | A | 0 | Claude Code |
| imagegenopenai/codex | Skill | 133k | yesterday | Apache-2.0 | A | 113 | Codex |
| playwright-climicrosoft/playwright | Skill | 99k | yesterday | Apache-2.0 | A | 19 | Claude Code |
| local-ai-agentsmicrosoft/ai-agents-for-beginners | Skill | 79k | 4d ago | MIT | A | 200 | Claude Code, Codex |
| systematic-debuggingobra/superpowers | Skill | 313k | 3d ago | MIT | A | 21 | Claude Code |
| next-cache-components-adoptionvercel/next.js | Skill | 143k | yesterday | MIT | A | 95 | Claude Code |
| next-partial-prefetching-adoptionvercel/next.js | Skill | 143k | yesterday | MIT | A | 103 | Claude Code |