Image optimization format selection and compression

Image optimization is crucial for web performance. Choosing the right format and compression method can significantly improve loading speed. Common formats have distinct characteristics: JPEG is suitable for photos, supports high compression but lacks transparency; PNG is ideal for icons and simple graphics, supports lossless compression and transparency but has larger file sizes; WebP combines the advantages of JPEG and PNG, offering higher compression and transparency but limited compatibility; AVIF has the highest compression but poorer compatibility. Format selection should consider content type and browser compatibility, and the `<picture>` element can provide fallback options. Image compression includes lossy and lossless methods, with common tools like command-line utilities, online tools, and build tool plugins. Responsive image optimization involves providing different sizes and using art direction. Advanced techniques include progressive JPEG, lazy loading, and CDN optimization. Performance monitoring can be done with tools like Lighthouse and WebPageTest. Future trends include new image formats and machine learning-based optimization.

Design of offline caching strategy

Offline caching is a key means to enhance application performance, especially in unstable or weak network environments. Reasonable caching strategies can significantly improve user experience. Front-end caching is mainly divided into memory caching, session storage, local storage, structured data storage, and network request interception caching. Cache update strategies include methods such as timed expiration and version number control. Hybrid caching strategy design adopts layered caching schemes and intelligent preloading strategies to improve hit rates. Cache cleanup mechanisms are based on LRU algorithms and storage space monitoring. Exception handling and fallback solutions ensure system reliability. Performance monitoring and tuning optimize strategies through hit rate statistics. Browser compatibility handling implements a unified caching interface to adapt to different environments.

Intelligent resource loading strategy

The core of intelligent resource loading strategy is to dynamically adjust the resource loading sequence and method based on the user's device network conditions and actual needs. Key steps include identifying above-the-fold critical resources and prioritizing them, using network APIs to detect connection speed and selecting resources of different quality, improving loading speed through preloading and preconnect techniques, applying lazy loading and on-demand loading for non-critical content, delivering adapted resources based on hardware capabilities like device memory and CPU cores, designing smart caching strategies to balance caching and updates, continuously monitoring performance metrics and dynamically adjusting strategies, and ultimately using a multi-dimensional decision function to comprehensively evaluate resource importance, visibility, network conditions, and other factors to determine whether to load. This strategy can significantly enhance page loading performance, reduce bandwidth waste, and optimize user experience.

Server Push technology

Server-side push technology allows the server to actively send data to the client, breaking the traditional HTTP request-response model. HTTP/2's Server Push feature is a typical implementation, enabling the delivery of static resources like CSS and JavaScript files. Its working principle is based on persistent connections and multiplexing. Key implementation technologies include HTTP/2 Server Push, WebSocket, Server-Sent Events (SSE), and GraphQL Subscriptions, each with its own advantages and disadvantages, making them suitable for different scenarios. Performance optimization involves metrics such as first-screen rendering time, network utilization, and bandwidth savings, along with cache strategies and priority control. Practical applications include real-time data dashboards, collaborative editing systems, and instant messaging apps. Advanced techniques encompass intelligent push, predictive push, cancellation mechanisms, and bandwidth-adaptive push. Common issue resolutions cover resource duplication, connection interruptions, and server-side resource management. Browser compatibility requires feature detection and fallback to traditional polling. Security considerations include authorization validation, data encryption, and DDoS protection. Monitoring and debugging can be achieved through developer tools, performance metrics, and server logs. Future trends focus on HTTP/3, the QUIC protocol, and the WebTransport API.

Optimization methods to eliminate redirect chains

A redirection chain refers to the process where a user's request for a URL results in multiple consecutive HTTP redirects from the server before reaching the target page, such as A to B to C to D. Each redirect adds a delay of 100–500 ms, and 40% of users abandon the visit if loading exceeds 3 seconds. Key impacts include increased load time, bandwidth consumption, reduced search engine efficiency, and negative effects on user experience metrics. Common scenarios include HTTP-to-HTTPS jumps, domain canonicalization, URL path adjustments, and tracking parameters. Server-side optimizations involve directly returning the final URL, consolidating redirect rules, and using HSTS headers. Front-end optimizations include preloading final resources and replacing redirects with the History API. Webpack configuration optimizations and CDN edge computing optimizations involve edge redirect rules and caching redirect responses. Mobile handling covers app links, universal links, and Android App Links. Monitoring uses the Navigation Timing API and log analysis with the ELK Stack. Advanced architecture design includes reverse proxy preprocessing and distributed configuration management. Special scenarios involve multilingual redirect optimization and A/B test分流.

The Domain Sharding strategy

Domain sharding is a technique that improves webpage loading performance by distributing resources across multiple subdomains. Browsers impose limits on the number of concurrent requests to the same domain, and by creating multiple subdomains, this restriction can be bypassed to enable parallel downloading of more resources. The article provides a detailed explanation of browser concurrent connection limits and how domain sharding works, covering DNS configuration, server setup, and frontend resource referencing methods. It also introduces automated sharding strategies, such as Webpack configuration, and best practices like selecting an appropriate number of subdomains and resource categorization strategies. Additionally, it analyzes the impact of HTTP/2 on domain sharding and modern alternatives like resource bundling and CDN usage. Finally, it discusses real-world case studies and performance monitoring, emphasizing the need to balance the number of shards based on specific scenarios to achieve optimal performance.

Resource preloading (preload/prefetch) technology

Resource preloading technology reduces user wait times by fetching critical resources in advance, primarily through two methods: preload and prefetch. Preload forces the browser to immediately load key resources for the current page, such as above-the-fold fonts and large images, while prefetch loads potentially needed resources (e.g., next-page content or popup scripts) during browser idle time. Practical applications require attention to resource priority control, cross-origin handling, and conditional responsive loading. Performance optimization case studies demonstrate specific solutions for addressing font flickering and single-page application route preloading. In terms of browser compatibility, mainstream modern browsers support it, but fallback strategies must be considered. Monitoring and evaluation can be achieved using the Resource Timing API. Advanced applications include dynamic preloading based on user behavior and Service Worker integration. Common pitfalls include excessive preloading and neglecting caching best practices. Recommendations suggest analyzing critical request chains and adopting progressive strategies. This technology can synergize with optimization techniques like HTTP/2 Server Push and lazy loading.

The advantages and applications of HTTP/2 and HTTP/3

HTTP2 significantly improves performance through multiplexing and header compression, resolving HTTP1.1's head-of-line blocking issue. HTTP3, based on the QUIC protocol, uses UDP for transport, enabling connection migration and better congestion control. E-commerce websites are well-suited for HTTP2, while video streaming benefits more from HTTP3 migration. Migrating to HTTP2 is simpler, but HTTP3 requires compatibility considerations. Performance monitoring and security configurations are critical for both protocols. Future evolution includes WebTransport and enhanced priority control, while edge computing combined with protocol innovation unlocks new use cases.

Reasonable use of CDN to accelerate static resources

The basic principle of CDN acceleration for static resources is to deploy edge node servers globally, caching resources closer to users to reduce latency and improve loading speed. Resources suitable for CDN acceleration include images, front-end static files, media files, and downloadable files. For CDN domain strategies, it is recommended to use multiple domains for parallel loading and subdomain partitioning to avoid cookie contamination. In terms of cache control, setting reasonable cache headers and using file fingerprinting techniques are advised. Advanced techniques include intelligent resource selection, pre-connect and pre-load, as well as edge computing processing. Performance monitoring can be achieved through the Performance API and real-user monitoring. For security, ensure HTTPS transmission and consider bandwidth cost optimization and anti-hotlinking measures.

Enable Gzip/Brotli compression technology

In modern web applications, the size of resource files directly impacts page loading speed. Gzip and Brotli, as mainstream compression algorithms, can significantly reduce the transmission size of text-based resources. By properly configuring server compression strategies, a compression rate of 50% to 70% can typically be achieved, which noticeably improves first-screen loading performance. Gzip is based on the DEFLATE algorithm, using LZ77 and Huffman coding, while Brotli employs a variant of LZ77 with second-order context modeling for higher efficiency. Server configuration requires setting compression levels and file types, and front-end builds can generate pre-compressed files. Proper handling of cache headers and content negotiation is crucial. Performance tests show that Brotli offers better compression ratios than Gzip but consumes more CPU time. The compression effect is more pronounced in mobile network environments, though browser compatibility and error handling must be considered. Advanced tuning includes optimizing specific content types and feature detection. Since browser support for compression algorithms varies, the choice should be made based on practical scenarios.