Precompressed

Precompressed refers to data that has already been compressed by a lossless compression algorithm before it is transmitted, stored, or further processed. Precompression contrasts with on-the-fly compression, where a system compresses data at the moment it is served or consumed.

In practice, precompression is common in content delivery networks and static sites, where build pipelines produce multiple precompressed versions of assets (for example gzip and Brotli) so servers can quickly serve the version that matches a client's accepted encoding without performing compression at request time.

Common algorithms include gzip, Brotli, and, in some contexts, Zstandard. The goal is to reduce bandwidth and response time, particularly for text-heavy assets such as HTML, CSS, and JavaScript, though images and other already-compressed formats are sometimes compressed as part of a broader optimization strategy.

Advantages include lower CPU usage at service time, faster initial response, and predictable compression ratios. Disadvantages include increased storage requirements for multiple variants, the complexity of update workflows, and potential inefficiency if assets are updated frequently or if the chosen algorithms do not compress well.

Management often involves build automation that generates and deploys precompressed copies, a content-encoding aware delivery mechanism that serves the best variant according to request headers, and cache strategies to ensure consistency across changes.