lazy loading
Deferring an image or frame until it is about to enter the viewport, by the loading=lazy attribute or by script.
What lazy loading does not show
It saves bandwidth below the fold and costs paint time above it: an image the page opens with that is marked lazy arrives later than it would have unmarked, and a script-only lazy loader shows a crawler nothing at all.
Related terms in HTTP, edge and rendering
The delivery layer between an origin and a client: proxies, caches, redirects, status codes and the headers that decide what a crawler actually received.
Link header · content negotiation · Markdown negotiation · Retry-After · Server-Timing · WWW-Authenticate · Allow header · Content-Digest · Origin server · Reverse proxy · CDN · Edge node · WAF · Bot score · TLS handshake · DNS resolution · DNS timeout · Connection timeout · Read timeout · Redirect chain · Redirect loop · 301 redirect · 302 redirect · 307 redirect · 308 redirect · 304 response · 404 response · 410 response · 429 response · 500 response · 502 response · 503 response · 504 response · HEAD request · GET request · Content type · MIME sniffing · Content encoding · Compression · Brotli · ETag · Last-Modified · If-None-Match · Cache hit · Cache miss · Cache key · Vary header · Stale response · Stale-while-revalidate · Edge redirect · Origin bypass · Response parity · Header parity · hreflang · canonical URL · HSTS · HSTS preload list · Content-Security-Policy · CSP nonce · edge cache · cache split · cache-buster · Cache-Control · Age header · render-blocking resource · payload text share · 404 and 410 status codes
Questions about lazy loading
What is lazy loading?
Deferring an image or frame until it is about to enter the viewport, by the loading=lazy attribute or by script.
What does lazy loading not show or guarantee?
It saves bandwidth below the fold and costs paint time above it: an image the page opens with that is marked lazy arrives later than it would have unmarked, and a script-only lazy loader shows a crawler nothing at all.
Which area of the glossary does lazy loading belong to?
HTTP, edge and rendering: The delivery layer between an origin and a client: proxies, caches, redirects, status codes and the headers that decide what a crawler actually received.
← payload text share · 404 and 410 status codes →
See it in the full glossary · 751 terms across 19 areas.