All levelsPronunciation#pronunciation#web-performance#core-web-vitals#ipa
Web Performance Metric Abbreviations
Core Web Vitals and performance metrics are essential vocabulary for frontend engineers and SEOs. Learn whether to say each metric letter-by-letter or as a word — and get the stress right every time.
0 / 5 completed
1 / 5
How do you pronounce TTFB (Time to First Byte)?
TTFB is pronounced letter-by-letter as 'tee-tee-ef-BEE' (/ˌtiːˌtiːˌɛfˈbiː/), an initialism for Time To First Byte. TTFB measures the time from when a user makes an HTTP request to when the first byte of the response is received — a key server performance indicator. Each letter is spoken separately with stress on the last: tee-tee-ef-BEE.
2 / 5
How do you pronounce LCP (Largest Contentful Paint)?
LCP is pronounced letter-by-letter as 'el-see-PEE' (/ˌɛlˌsiːˈpiː/), initialism for Largest Contentful Paint. LCP is a Core Web Vital that measures how long it takes for the largest visible element on a page to render — a key indicator of perceived load speed. Google uses LCP as a ranking signal. Letters spoken separately: el-see-PEE.
3 / 5
How do you pronounce CLS (Cumulative Layout Shift)?
CLS is pronounced letter-by-letter as 'see-el-ES' (/ˌsiːˌɛlˈɛs/), initialism for Cumulative Layout Shift. CLS is a Core Web Vital that measures visual stability — how much page elements unexpectedly move during loading. A low CLS score means users are not clicking the wrong thing because content jumped. Letters spoken separately: see-el-ES.
4 / 5
How do you pronounce INP (Interaction to Next Paint)?
INP is pronounced letter-by-letter as 'eye-en-PEE' (/ˌaɪˌɛnˈpiː/), initialism for Interaction to Next Paint. INP replaced FID as a Core Web Vital in 2024, measuring the latency of all user interactions with a page rather than just the first one. It captures the overall responsiveness of a page throughout its lifecycle. Letters: eye-en-PEE.
5 / 5
How do you pronounce RAIL (performance model by Google)?
RAIL is pronounced 'RAYL' (/reɪl/), like the English word for a rail or railway track — one syllable. RAIL is a user-centric performance model by Google standing for Response, Animation, Idle, and Load. Unlike most acronyms, RAIL is spoken as a single word because it forms a pronounceable word. The model provides performance goals for each phase of app interaction.