Definitions beginning with F

FaaS

Function as a Service: executing functions on demand without directly managing a permanent server.

In practice: Measure function frequency, duration and dependencies before comparing costs.

Faceted navigation

Navigation combining several filters and potentially generating many URLs from selected categories, attributes or sort orders.

In practice: test useful filter combinations and inspect the URLs they create.

Fallback font

Font used when a preferred font is unavailable or lacks a character. Check metrics and glyphs: substitution can alter line wrapping and layout.

Reference: MDN : font-family

Source consulted : MDN · 2026-10-17

Test headings, prices and paragraphs before the main font loads, using the languages actually published.

FAQ review date

Scheduled or recorded point for checking whether a FAQ answer remains accurate after a change in price, service or rule.

In practice: review the answer whenever a mentioned price, deadline or service changes.

Favicon

Small icon associated with a website and used in places such as browser tabs and bookmarks. It helps identify a page among others at a size where detail quickly disappears. It complements the page title and should not be the sole carrier of essential information.

Reference: MDN : Favicon · Source consulted 2026-10-18

In practice: compare the icon in light and dark tabs and in a bookmark. Check its actual small-size appearance and file loading; a logo legible at large sizes may become an indistinct mark in the browser bar.

Feature flag

Mechanism enabling or disabling a feature without requiring a complete new code deployment.

In practice: record the owner, activation condition and intended removal date.

Featured snippet

Highlighted search-result excerpt providing a quick answer, generally with a link to the source.

In practice: Put a clear answer near the question it addresses, then observe actual search presentation.

FID

First Input Delay was a metric for the delay before processing the first interaction. INP replaced it among Core Web Vitals; retain this distinction when reading historical reports.

Reference: web.dev : First Input Delay · Source consulted 2026-10-18

In practice: Recognise this older metric in historical reports and use current measures for decisions.

Field data

Measurements collected during real visits under observed users’ conditions. They describe a specific population and period; public CrUX data does not automatically cover all browsers or pages.

Reference: Chrome : UX Report · Source consulted 2026-10-18

In practice: check period, volume and device type before comparing real users with lab tests.

Field error message

Text associated with rejected input that identifies the problem and helps correction. Distinguish invalid format from processing failure, and avoid unnecessarily clearing other valid answers.

Reference: W3C WAI : Validating input · Source consulted 2026-10-18

In practice: name the field, problem and correction.

Figma

Collaborative tool for interface design, prototyping and design systems.

In practice: Connect mockup components, interaction states and real content to avoid incomplete specifications.

Firewall

Firewall filtering network communications according to rules to block unwanted access or behavior.

Reference: NIST CSRC · Firewall · Source consulted 2026-10-31

In practice: Link each rule to a known need and review it when the service changes.

First Contentful Paint

FCP measures the delay until content such as text or an image first appears. It marks a visible beginning, not readiness of the main content or interface responsiveness.

Reference: web.dev : First Contentful Paint · Source consulted 2026-10-18

In practice: Measure this first paint alongside later journey steps; it does not prove the page is usable.

First-party data

Data collected directly by an organization from its audience or customers within its own relationship.

In practice: Tell people why data is collected and review later uses.

Focal point

The important image area to preserve when cropping. Content alignment, for example with object-position, helps retain the subject; also check narrow layouts and captions.

Reference: MDN : object-position · Source consulted 2026-10-18

In practice: Keep the important subject inside an area that survives card and mobile crops.

font-display

CSS descriptor governing text display while a font loads. Its choice affects waiting, fallback and swapping; it does not fix an oversized font file.

Reference: MDN : font-display

Source consulted : MDN · 2026-10-17

Observe the page on a slow connection and with the font unavailable; check readability and text movement.

Form validation

Checking required values, formats and applicable rules in form data. The browser can help correct input, while the server must validate what it receives. A correctly formatted value, such as an email address, is not thereby confirmed as accurate.

Reference: MDN : HTML constraint validation · Source consulted 2026-10-18

In practice: preserve entered values on error, identify the field to correct and validate again on the server.

Framework

Software framework providing structure, conventions and reusable components for application development.

In practice: Assess maintenance, supported versions and available skills before adopting it.

Frequently asked question

Question repeatedly observed among an audience and answered in verifiable editorial content.

In practice: record where the question actually came from before writing its answer.

Front-end

The part of a site presented and used in a browser, including structure, styles and interactions. It must reflect actual service states; a successful interface does not guarantee server processing.

Reference: MDN : Client-server overview · Source consulted 2026-10-18

In practice: Test loading, error and success states with real content.

FTP

File Transfer Protocol: an older file-transfer protocol. SFTP or other encrypted solutions are preferable for sensitive access.

In practice: Check the required transfer method and use an encrypted option for sensitive files.

Funnel

Funnel representing the gradual reduction in people from discovery through interest, consideration and conversion.

In practice: Check whether leaving the funnel is truly abandonment rather than another route to the goal.