Donaldson R F
Linux, Web Server & Database
Enable GZIP Compression
Turn on GZIP compression on your web server to cut page load times and bandwidth.
The Problem
Your website transfers uncompressed HTML, CSS and JavaScript to every visitor, making pages noticeably slower to load than necessary, especially on slower connections — and GZIP compression often isn't switched on by default.
About this problem
GZIP compression shrinks text-based content (HTML, CSS, JS, JSON) significantly before sending it over the network, often by 60-80%, which visitors experience as a faster-loading site with no visible change otherwise — it's one of the simplest, lowest-risk performance wins available on a web server.
This gets missed because it's not always enabled by default, and some setups only compress certain file types while leaving others (like JSON API responses) uncompressed.
What's Included
- Enabling GZIP compression at the web server level for appropriate text-based file types
- Setting a sensible compression level balancing CPU use against file size savings
- Confirming compression is actually being applied with a real test, not just assumed from config
- Checking that already-compressed files (images, videos) are correctly excluded
What's NOT Included
- Brotli compression specifically (see the separate Brotli service, which generally compresses better)
- CDN-level compression configuration
- Application-level response optimisation beyond server-level compression
How It Works
- Check current response headers to confirm whether compression is already active or not.
- Enable the gzip module/directive at the web server level (Nginx's gzip on, or Apache's mod_deflate).
- Configure which MIME types should be compressed (HTML, CSS, JS, JSON, SVG) while excluding already-compressed formats like JPEG.
- Set an appropriate compression level, balancing CPU overhead against the size reduction achieved.
- Test with a real request and check the Content-Encoding: gzip response header to confirm it's genuinely active.
In practice: you buy the service, send over whatever access or details the job needs, I investigate and do the work, and you confirm it's resolved before we call it done.
Frequently Asked Questions
- What does GZIP compression actually do?
- It compresses text-based files like HTML, CSS and JavaScript before sending them to the visitor's browser, which then decompresses them automatically — resulting in less data transferred and faster page loads.
- How do I check if GZIP is already enabled on my site?
- Checking the response headers for a page (via browser dev tools or a command-line request) for Content-Encoding: gzip shows whether it's actively compressing responses.
- Will GZIP compression slow down my server?
- Compressing content does use a small amount of extra CPU, but for nearly all sites the bandwidth and load-time savings far outweigh that cost, especially with a sensible compression level chosen.
- Should I compress images with GZIP too?
- No — image formats like JPEG and PNG are already compressed internally, so running GZIP over them wastes CPU for little to no size benefit; they should be excluded from the compression rule.
- Does GZIP compression affect SEO?
- Indirectly yes, since faster page load times are a known ranking factor and also improve the user experience metrics search engines increasingly weigh.
- What's the difference between GZIP and Brotli?
- Brotli is a newer compression algorithm that generally achieves better compression ratios than GZIP for the same content, though GZIP has slightly broader legacy browser support.