How deeply does CSS in Depth, Second Edition cover fallback?

Explains the visible loading sequence and connection-speed trade-offs, but defers deeper web-font performance treatment.

Fallback

As explained in CSS in Depth, Second Edition

Fallback is the font-display value that permits a brief invisible-text period, then uses the fallback font until the web font loads.

A web font can leave text invisible while it loads or show a fallback font before switching. Set `font-display: fallback` inside an `@font-face` rule to take a middle course: text is invisible briefly, then appears in the fallback font if the web font is not ready. When the web font loads, it replaces the fallback font. section 12.5.1

Choose the loading behavior to fit the connection and the design:

`fallback` works well on fast connections, where the brief invisible period may end before a font switch is visible. If loading takes longer than about 100 ms, readers may see the fallback font switch to the web font. section 12.5.1
`swap` shows the fallback font immediately, making it a better choice on slow connections. `optional` can keep the fallback font when loading takes too long, which suits a web font that is less vital to the design. section 12.5.1

Changing a Google Fonts loading choice

A Google Fonts stylesheet URL with `&display=swap` produces `font-display: swap` rules. Change that parameter to `&display=fallback` to use the brief invisible period instead of showing the fallback font immediately. section 12.5.1

How CSS in Depth, Second Edition covers it

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Also explained in

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The Art of CodeA fallback is an alternative behavior or result selected when the preferred operation is unavailable or unsuccessful.
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Natural Language Processing in Action, Second EditionA fallback response is a predefined chatbot reply provided when no recognized intent meets the required confidence level.
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Prompt Engineering in PracticeA predefined response or processing path used when input is malformed, incomplete, invalid, or manipulated.
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Machine Learning System DesignA fallback is an alternative behavior or implementation used when the primary behavior or system cannot operate normally.
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Effective Conversational AIA fallback path is a conversational handling route for input that cannot be understood or handled by the primary flow.
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React Hooks in Action: With Suspense and Concurrent ModeA fallback is alternate user-interface content displayed while the intended content is unavailable or an error has occurred.
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Tiny CSS ProjectsAn image fallback is an alternative presentation or behavior provided when an image resource fails to load.
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Grokking AI ApplicationsA prompt instruction that specifies an alternative response when the model cannot complete the requested task or find the requested information.
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Quarkus in ActionA fallback is a fault-tolerance pattern that supplies an alternate result or behavior when an operation fails.
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AI Agents in Action, Second EditionA fallback is an alternative action or implementation used when the preferred operation cannot complete successfully.
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LLMs in ProductionA fallback response is a predefined response returned when processing a user request fails.
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Build AI-Enhanced Web AppsA user-facing fallback is an alternative interface response or recovery option presented when the intended operation fails.
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Machine Learning Platform EngineeringA fallback strategy defines an alternative provider, model, or execution path used when the preferred path fails or cannot satisfy a request.
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Generative AI in ActionA fallback mechanism is an alternative execution or service path invoked when the preferred path fails or becomes unavailable.

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Related concepts

routingcontrasts with · Routing is the selection of a path, destination, or processing component to direct an item, request, or flow toward an intended endpoint.
rule-based systemuses · A rule-based system produces outputs or actions by applying explicitly specified rules or conditions to inputs or represented facts.
Llamauses · Llama is a family of autoregressive large language models developed by Meta and released in multiple versions and sizes.

This explainer was generated by Manning's knowledge graph from the text of CSS in Depth, Second Edition. The section links point to the parts of the book it draws on.