शब्दकोश · परफ़ॉर्मेंसAbove the FoldAbove the fold is the part of a web page visible without scrolling, which should load first because it shapes a visitor's first impression of speed.शब्दकोश · परफ़ॉर्मेंसAutoscalingAutoscaling automatically adds or removes servers or containers in response to measured load, matching capacity to demand without manual intervention.शब्दकोश · परफ़ॉर्मेंसBackpressureBackpressure is a signal from a slow consumer telling producers to slow down, preventing queues and memory from growing until a system collapses.शब्दकोश · परफ़ॉर्मेंसBrotli CompressionBrotli is a compression algorithm from Google that usually shrinks text assets 15-25 percent more than gzip and is supported by all modern browsers.शब्दकोश · परफ़ॉर्मेंसCache BustingCache busting changes a file's URL when its content changes, so browsers and CDNs fetch the new version despite long cache lifetimes.शब्दकोश · परफ़ॉर्मेंसCache Hit RatioCache hit ratio is the share of requests served from a cache rather than the origin server, a key measure of CDN and caching effectiveness.शब्दकोश · परफ़ॉर्मेंसCache InvalidationCache invalidation is removing or refreshing cached content when the source data changes, so users stop receiving outdated copies from caches and CDNs.शब्दकोश · परफ़ॉर्मेंसCache StampedeA cache stampede happens when a popular cache entry expires and many requests rebuild it at once, flooding the database or origin behind the cache.शब्दकोश · परफ़ॉर्मेंसCapacity PlanningCapacity planning is forecasting how much compute, memory, storage and bandwidth you will need so traffic growth never outpaces your infrastructure.शब्दकोश · परफ़ॉर्मेंसCDN (Content Delivery Network)A CDN is a geographically distributed network of servers that caches your content close to visitors, reducing latency and shielding your origin from load.शब्दकोश · परफ़ॉर्मेंसCLS (Cumulative Layout Shift)CLS is a Core Web Vitals score that totals unexpected layout shifts during a page's life, showing how visually stable the page is for users.शब्दकोश · परफ़ॉर्मेंसCode SplittingCode splitting breaks a JavaScript bundle into smaller chunks that load on demand, so visitors download only the code a page or feature needs.शब्दकोश · परफ़ॉर्मेंसCold StartA cold start is the extra delay when a function, container, or cache has to initialize from scratch before it can serve its first request.शब्दकोश · परफ़ॉर्मेंसCompression RatioCompression ratio compares a file's original size with its compressed size, showing how much a method like gzip or Brotli reduces transferred bytes.शब्दकोश · परफ़ॉर्मेंसConditional RequestA conditional request is an HTTP request with headers like If-None-Match that lets a server answer 304 Not Modified instead of resending an unchanged file.शब्दकोश · परफ़ॉर्मेंसConnection TimeConnection time is the delay to establish a TCP connection, plus TLS for HTTPS, before the first byte of an HTTP request can be sent.शब्दकोश · परफ़ॉर्मेंसCritical Rendering PathThe critical rendering path is the sequence of steps a browser takes to turn HTML, CSS and JavaScript into pixels on screen.शब्दकोश · परफ़ॉर्मेंसDNS Lookup TimeDNS lookup time is how long it takes to resolve a hostname to an IP address before a connection can start, often 20-120 ms on a cold cache.शब्दकोश · परफ़ॉर्मेंसEarly Hints (103)HTTP 103 Early Hints is an informational response that lets a server send Link headers before the final response so browsers can preload resources sooner.शब्दकोश · परफ़ॉर्मेंसETag (Entity Tag)An ETag is an HTTP response header holding a version identifier for a resource, letting clients revalidate cached copies and receive 304 Not Modified.शब्दकोश · परफ़ॉर्मेंसFCP (First Contentful Paint)FCP is the time from navigation start until the browser renders the first piece of DOM content, such as text, an image or a non-white canvas.शब्दकोश · परफ़ॉर्मेंसFID (First Input Delay)FID measured the delay between a user's first click or tap and the moment the browser could start handling it; it was retired in favor of INP.शब्दकोश · परफ़ॉर्मेंसField Data vs Lab DataField data is performance measured from real users' visits, while lab data comes from controlled, repeatable synthetic tests; each answers different questions.शब्दकोश · परफ़ॉर्मेंसFont Loading (FOIT and FOUT)Font loading behavior decides what users see while web fonts download: invisible text (FOIT), or fallback text that swaps to the web font (FOUT).शब्दकोश · परफ़ॉर्मेंसGzip CompressionGzip is a widely supported compression format that web servers use to shrink text responses such as HTML, CSS and JavaScript before sending them.शब्दकोश · परफ़ॉर्मेंसHAR File (HTTP Archive)A HAR file is a JSON export of every request and response a browser made while loading a page, used to debug slow loads and failed requests.शब्दकोश · परफ़ॉर्मेंसHead-of-Line BlockingHead-of-line blocking happens when one delayed or lost item at the front of a queue holds up everything behind it, slowing HTTP/1.1 and TCP connections.शब्दकोश · परफ़ॉर्मेंसHotlinkingHotlinking is embedding another site's image, video or file directly from its server, so the owner pays the bandwidth when your page loads it.शब्दकोश · परफ़ॉर्मेंसHTTP CachingHTTP caching lets browsers and CDNs reuse stored responses, controlled by headers like Cache-Control, ETag and Last-Modified, to avoid repeat downloads.शब्दकोश · परफ़ॉर्मेंसHTTP Keep-Alive (Persistent Connections)HTTP keep-alive reuses one TCP connection for several requests instead of opening a new one each time, saving handshakes and cutting page load latency.शब्दकोश · परफ़ॉर्मेंसHTTP/2HTTP/2 is the second major HTTP version, multiplexing many requests over one connection with header compression to load pages faster than HTTP/1.1.शब्दकोश · परफ़ॉर्मेंसHTTP/3 and QUICHTTP/3 runs HTTP over QUIC, a UDP-based transport with built-in TLS 1.3, avoiding TCP head-of-line blocking and speeding up connections on lossy networks.शब्दकोश · परफ़ॉर्मेंसImage OptimizationImage optimization reduces image bytes without visible quality loss through modern formats, correct sizing, compression and caching to speed up pages.शब्दकोश · परफ़ॉर्मेंसINP (Interaction to Next Paint)INP measures how quickly a page visually responds to clicks, taps and key presses across a whole visit, and replaced FID as a Core Web Vital.शब्दकोश · परफ़ॉर्मेंसJavaScript Bundle SizeJavaScript bundle size is the number of bytes of script a page ships, both compressed for transfer and uncompressed, which affects download and parse time.शब्दकोश · परफ़ॉर्मेंसLatencyLatency is the delay between sending a request and receiving the first part of a response, often measured as network round-trip time in milliseconds.शब्दकोश · परफ़ॉर्मेंसLCP (Largest Contentful Paint)LCP is the time from navigation start until the largest image or text block in the viewport finishes rendering, a Core Web Vitals loading metric.शब्दकोश · परफ़ॉर्मेंसLighthouse ScoreThe Lighthouse performance score is a 0-100 rating computed from weighted lab metrics such as LCP, TBT and CLS, run in a simulated environment.शब्दकोश · परफ़ॉर्मेंसLoad SheddingLoad shedding deliberately rejects some requests during overload, often with a 503, so the system can keep serving the rest quickly instead of collapsing.शब्दकोश · परफ़ॉर्मेंसLoad TestingLoad testing simulates expected and peak numbers of concurrent users against a system to measure response time, error rate, and capacity before real traffic arrives.शब्दकोश · परफ़ॉर्मेंसLong TaskA long task is any piece of main-thread work that runs for more than 50 milliseconds, blocking the browser from responding to user input in the meantime.शब्दकोश · परफ़ॉर्मेंसMain Thread (Browser)The browser main thread is the single thread that runs a page's JavaScript, handles input events, calculates styles and layout, and paints.शब्दकोश · परफ़ॉर्मेंसOrigin ShieldOrigin shield is a CDN layer that funnels cache misses from many edge locations through one regional cache, reducing requests that reach your origin server.शब्दकोश · परफ़ॉर्मेंसPage Load TimePage load time is how long a page takes to become usable, commonly measured as the load event, but better described by several user-centered metrics.शब्दकोश · परफ़ॉर्मेंसPage WeightPage weight is the total size in bytes of all resources a page downloads, including HTML, CSS, JavaScript, images, fonts and media.शब्दकोश · परफ़ॉर्मेंसPageSpeed InsightsPageSpeed Insights is Google's free tool that reports a URL's real-user Core Web Vitals from CrUX alongside a Lighthouse lab test with fix suggestions.शब्दकोश · परफ़ॉर्मेंसPoint of Presence (PoP)A point of presence is a physical location where a CDN or network provider keeps servers close to users to cut latency and offload your origin.शब्दकोश · परफ़ॉर्मेंसPreconnect (rel=preconnect)rel=preconnect tells the browser to open a connection to another origin early, completing DNS, TCP and TLS before any request is made there.शब्दकोश · परफ़ॉर्मेंसPrefetch (rel=prefetch)rel=prefetch is a low-priority hint asking the browser to download a resource during idle time because it will likely be needed on a later navigation.शब्दकोश · परफ़ॉर्मेंसPreload (rel=preload)rel=preload is a resource hint that tells the browser to fetch a specific file early, at high priority, because the current page will need it soon.शब्दकोश · परफ़ॉर्मेंसRender-Blocking ResourceA render-blocking resource is a CSS or synchronous JavaScript file the browser must fetch and process before it can paint any page content.शब्दकोश · परफ़ॉर्मेंसRequest TimeoutA request timeout is the maximum time a client, proxy or server waits for a complete request or response before giving up and returning an error.शब्दकोश · परफ़ॉर्मेंसSoak TestingSoak testing runs a steady, moderate load for many hours or days to expose memory leaks, resource exhaustion, and slow degradation that short tests miss.शब्दकोश · परफ़ॉर्मेंसSpeed IndexSpeed Index is a lab metric that scores how quickly the visible part of a page is populated during load, based on frame-by-frame visual progress.शब्दकोश · परफ़ॉर्मेंसstale-if-errorstale-if-error is a Cache-Control extension that lets a cache serve an expired response when the origin returns an error, instead of passing the error on.शब्दकोश · परफ़ॉर्मेंसStale-While-RevalidateStale-while-revalidate is a Cache-Control extension that serves a stale cached response immediately while fetching a fresh copy in the background.शब्दकोश · परफ़ॉर्मेंसStress TestingStress testing pushes a system beyond its expected capacity to find the breaking point and to see how it fails and recovers.शब्दकोश · परफ़ॉर्मेंसTail LatencyTail latency is the response time experienced by the slowest requests, usually the 99th percentile or above, and it often defines the real user experience.शब्दकोश · परफ़ॉर्मेंसTBT (Total Blocking Time)TBT is a Lighthouse lab metric that sums the portion of each long task beyond 50 ms between FCP and Time to Interactive, estimating main-thread blocking.शब्दकोश · परफ़ॉर्मेंसTCP Slow StartTCP slow start is a congestion control phase where a new connection starts with a small send window and roughly doubles it each round trip.शब्दकोश · परफ़ॉर्मेंसThird-Party ScriptA third-party script is JavaScript loaded from a domain you do not control, such as analytics, ads, chat widgets or tag managers, often slowing a page.शब्दकोश · परफ़ॉर्मेंसThundering HerdA thundering herd is a surge of simultaneous requests or retries that hits a server at once, usually right after a restart, cache expiry, or outage ends.शब्दकोश · परफ़ॉर्मेंसTTFB (Time to First Byte)TTFB measures the time from starting a request until the first byte of the response arrives, covering DNS, connection, TLS and server work.शब्दकोश · परफ़ॉर्मेंसTTI (Time to Interactive)Time to Interactive was a Lighthouse metric marking when a page looked loaded and reliably responded to input; it was removed from scoring in Lighthouse 10.शब्दकोश · परफ़ॉर्मेंसUSE MethodThe USE method checks every resource for Utilization, Saturation and Errors to find performance bottlenecks quickly.शब्दकोश · परफ़ॉर्मेंसVary HeaderThe Vary response header lists request headers that change the response, telling caches to store separate copies for each variation, such as Accept-Encoding.शब्दकोश · परफ़ॉर्मेंसWaterfall Chart (Network)A network waterfall chart shows every request a page makes as a horizontal bar on a timeline, revealing delays in DNS, connection, waiting and download.