igorvaryvoda Image Optimization Expert
Default Workflow
- Inspect the real surface before prescribing changes: rendered HTML, framework image components, network waterfall, build output, CDN URLs, and asset inventory.
- Identify the page role of each important image: LCP/hero, above-fold content, product/gallery, thumbnail/list item, CSS background, decorative, user-uploaded, or source/master asset.
- Fix the highest-impact path first: LCP delivery, oversized images, missing dimensions, wrong format, missing responsive candidates, unnecessary client-side resizing, or CDN bypass.
- Keep source quality high and delivery variants cheap: preserve master assets, transform at the CDN/build edge, and avoid destructive re-encoding loops.
- Verify with evidence: rendered markup, response headers/content type, decoded/displayed size, Lighthouse/WebPageTest/DevTools, and visual inspection for artifacts.
When a repo/app is available, make the patch instead of only giving advice. Prefer local framework conventions over generic snippets.
Fast Audit Checklist
- LCP: Hero image is not lazy loaded, has
fetchpriority="high"or framework priority, is preloaded when appropriate, comes from a fast origin/CDN, and is right-sized for the rendered slot. - CLS: Every meaningful image has intrinsic
widthandheightor a stable CSSaspect-ratio. - Responsive delivery: Width-based
srcsetuses realistic layoutsizes; CSS/background images have equivalent responsive handling. - Formats: Use negotiated/modern formats (
format=optimal, AVIF/WebP, or framework auto format) with safe fallbacks. - Compression: Quality is content-aware, not universally maxed out; product/face/detail images get higher quality than thumbnails/backgrounds.
- Loading: Below-fold images are lazy and async-decoded; above-fold images are eager and not hidden behind slow JS.
- CDN/cache: Image URLs are cacheable and transformation params are stable; source files are not repeatedly transformed by multiple layers.
- Accessibility/SEO: Informative images have useful alt text; decorative images use empty alt; product assets can preserve metadata in CMS/CDN records even if delivery strips EXIF.
Use The Audit Script
For HTML files or public URLs, run the bundled no-dependency audit before and after changes. The script lives in this skill's own scripts/ directory — resolve it from the skill's base directory (shown when this skill loads), not the target project:
node <skill-base-dir>/scripts/audit-images.mjs ./dist/index.html
node <skill-base-dir>/scripts/audit-images.mjs --head https://example.com/
node <skill-base-dir>/scripts/audit-images.mjs --json https://example.com/ > image-audit.json
The script checks image markup, srcset/sizes, preload hints, likely LCP mistakes, Sirv URL usage, and optional HTTP headers/content length.
Decision Matrix
| Situation | Preferred Action |
|---|---|
| Static/project-owned images | Generate responsive variants at build time or move masters to an image CDN. |
| User-uploaded or product catalog images | Use an image CDN/API pipeline; do not commit generated variants into the app repo. |
| Existing Sirv account or Sirv URLs | Use Sirv dynamic imaging/profile/API workflows; read sirv-workflows.md. |
| Product gallery, zoom, 360 spin, video/model viewer, or smart gallery | Use ../sirv-media-viewer/SKILL.md before hand-building gallery behavior. |
| Next.js app | Prefer next/image; use a custom loader for external image CDNs when the CDN should transform. |
| CSS background hero | Consider replacing with semantic <img>/picture; if it must remain CSS, use image-set() and preload carefully. |
| Image quality problem | Compare candidate qualities visually and with SSIM/VMAF/Butteraugli where possible. |
| Need background removal, upscaling, product lifestyle, or alt text at scale | Use sirv-ai-studio when available; keep delivery concerns in Sirv/CDN workflow. |
When To Read References
- Sirv implementation workflows: CDN migration, dynamic URLs, profiles, REST inventory/upload/search, Next.js loader, verification: sirv-workflows.md
- Format details: browser support, encoding options, SVG security, HDR/wide gamut: formats.md
- Compression and quality: quality settings, metadata, batch processing, SSIM/VMAF: optimization.md
- Responsive images:
srcset,sizes, art direction, priorities, container queries, backgrounds: responsive.md - Performance: LCP/CLS/INP, placeholders, preload, budgets, measurement: performance.md
- Tools and services: Sirv, Cloudinary, imgix, CLI/build tools, Sharp/libvips: tools.md
Also load sibling skills when the task crosses into their specialty:
../video-optimization/SKILL.mdfor hero/background video, GIF-to-video, streaming, and video embeds.../sirv-dynamic-imaging/SKILL.mdfor Sirv URL parameters, profiles, crops, overlays, and caching.../sirv-api/SKILL.mdfor Sirv auth, file upload/fetch, search, metadata, jobs, usage limits.../sirv-media-viewer/SKILL.mdfor Sirv Media Viewer markup, JS loading, smart galleries, zoom/spin/video/model/PDF galleries, viewer API/events, accessibility, CSP, and performance.../sirv-ai-studio/SKILL.mdfor AI processing, MCP tools, background removal, upscaling, generation, product workflows, and alt text.
Default Recommendations
| Use Case | Format/Delivery Default |
|---|---|
| Photos and product images | AVIF/WebP via auto negotiation; JPEG fallback when needed. |
| Graphics/logos/icons | SVG when trusted and simple; otherwise WebP/PNG as needed. |
| Screenshots/text-heavy raster images | WebP lossless/near-lossless or optimized PNG. |
| Short animations | Animated WebP or video; avoid large GIFs. |
| High-value hero/product detail | Slightly higher quality, explicit dimensions, responsive candidates, CDN edge delivery. |
| Thumbnails/list media | Aggressive resizing, lower quality, lazy loading, stable aspect ratio. |
Quality starting points:
| Format | Starting Quality |
|---|---|
| JPEG | 75-85, higher for product/detail |
| WebP | 75-85 lossy; lossless for sharp graphics |
| AVIF | 60-75 for most photos |
| PNG | Lossless, then optimize or convert when safe |
Common Mistakes To Catch
- Lazy-loading the LCP image.
- Missing dimensions/aspect ratio.
- Serving a 2-4K image into a small card or mobile slot.
- Writing
sizes="100vw"for images that render in a 33-50vw grid. - Combining framework optimization and CDN transformations in ways that double-compress or block caching.
- Hard-coding AVIF/WebP without a fallback or content negotiation path.
- Using PNG for photos or JPEG for transparency/sharp text.
- Treating
alttext, filename, CDN metadata, and visible captions as interchangeable. - Fixing source assets but failing to verify rendered output and response headers.