Bolt performance

Font Loading Causing Layout Shift - FOUT or FOIT

Fonts load slowly causing text to flash or shift layout (Cumulative Layout Shift). Users see unstyled text briefly before custom font loads.

This impacts Core Web Vitals and user experience.

Error Messages You Might See

Cumulative Layout Shift > 0.25 Font blocking render for 3+ seconds Text remains invisible while custom font loads FOUT/FOIT causing layout thrashing
Cumulative Layout Shift > 0.25Font blocking render for 3+ secondsText remains invisible while custom font loadsFOUT/FOIT causing layout thrashing

Common Causes

  1. Loading fonts from CDN without preload
  2. Large font files not optimized or subsetted
  3. Font-display not set to optimal value
  4. Loading too many font variations
  5. Self-hosted fonts not configured for preload

How to Fix It

Add preload to head:

Use font-display: swap in @font-face to prevent invisible text

Subset fonts: include only characters you use

Use Next.js font optimization: import { Poppins } from 'next/font/google'

Limit to 2-3 font families max

Real developers can help you.

rayush33 rayush33 JavaScript (React.js, React Native, Node.js) Developer with demonstrated industry experience of 4+ years, actively looking for opportunities to hone my skills as well as help small-scale business owners with solutions to technical problems Omar Faruk Omar Faruk As a Product Engineer at Klasio, I contributed to end-to-end product development, focusing on scalability, performance, and user experience. My work spanned building and refining core features, developing dynamic website templates, integrating secure and reliable payment gateways, and optimizing the overall system architecture. I played a key role in creating a scalable and maintainable platform to support educators and learners globally. I'm enthusiastic about embracing new challenges and making meaningful contributions. Prakash Prajapati Prakash Prajapati I’m a Senior Python Developer specializing in building secure, scalable, and highly available systems. I work primarily with Python, Django, FastAPI, Docker, PostgreSQL, and modern AI tooling such as PydanticAI, focusing on clean architecture, strong design principles, and reliable DevOps practices. I enjoy solving complex engineering problems and designing systems that are maintainable, resilient, and built to scale. Franck Plazanet Franck Plazanet I am a Strategic Engineering Leader with over 8 years of experience building high-availability enterprise systems and scaling high-performing technical teams. My focus is on bridging the gap between complex technology and business growth. Core Expertise: šŸš€ Leadership: Managing and coaching teams of 15+ engineers, fostering a culture of accountability and continuous improvement. šŸ—ļø Architecture: Enterprise Core Systems, Multi-system Integration (ERP/API/ETL), and Core Database Structure. ā˜ļø Cloud & Scale: AWS Expert; architected systems handling 10B+ monthly requests and managing 100k+ SKUs. šŸ“ˆ Business Impact: Aligning tech strategy with P&L goals to drive $70k+ in monthly recurring revenue. I thrive on "out-of-the-box" thinking to solve complex technical bottlenecks and am always looking for ways to use automation to improve business productivity. Pratik Pratik SWE with 15+ years of experience building and maintaining web apps and extensive BE infrastructure Kingsley Omage Kingsley Omage Fullstack software engineer passionate about AI Agents, blockchain, LLMs. Bastien Labelle Bastien Labelle Full stack dev w/ 20+ years of experience MFox MFox Full-stack professional senior engineer (15+years). Extensive experience in software development, qa, and IP networking. Richard McSorley Richard McSorley Full-Stack Software Engineer with 8+ years building high-performance applications for enterprise clients. Shipped production systems at Walmart (4,000+ stores), Cigna (20M+ users), and Arkansas Blue Cross. 5 patents in retail/supply chain tech. Currently focused on AI integrations, automation tools, and TypeScript-first architectures. Tejas Chokhawala Tejas Chokhawala Full-stack engineer with 5 years experience building production web apps using React, Next.js and TypeScript. Focused on performance, clean architecture and shipping fast. Experienced with Supabase/Postgres backends, Stripe billing, and building AI-assisted developer tools.

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Frequently Asked Questions

What's the best font-display value?

swap: shows system font immediately, updates when custom loads (best UX). fallback: wait 100ms then show system

Should I self-host or use CDN?

Self-host for control and speed. CDN (Google Fonts) if you want simplicity

How do I minimize font downloads?

Subset fonts to used characters, use variable fonts for multiple weights, limit to necessary fonts

Related Bolt Issues

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