Reducing HTTP requests is one of the few performance changes that shows up as a felt difference rather than a number buried in a dashboard, because every image, stylesheet, font and script your page pulls in adds a small delay before anything on screen finishes loading. On a product page with a dozen thumbnails, three fonts and a handful of tracking scripts, those small delays add up into the wait a customer actually notices before they can scroll or tap anything.
None of this is about chasing a perfect score in some testing tool. It is about the handful of requests doing the least useful work being the easiest ones to cut, combine or delay, and the rest being left alone because they are already earning their place on the page.
What actually counts as an HTTP request
Every separate file a browser has to fetch to render a page counts: each image, each stylesheet, each font file, each script, even the small icon shown in the browser tab. A product page that loads twenty small icons one at a time is not obviously different from one that loads a single sprite sheet containing the same icons, right up until you count how many separate round trips to the server each approach costs, and the numbers stop looking similar quite quickly.
The order matters as much as the count. A script sitting near the top of the page that blocks everything below it from rendering does more damage than the same script sitting near the bottom, even though both count as exactly one request. Fixing the count without fixing the order leaves the slowest part of the page exactly where it was.
Where reducing HTTP requests pays off fastest
Reducing HTTP requests matters most on the pages a customer has to get through before they can buy anything, which for most shops means the product page and the basket, not the blog or the about page sitting three clicks away. A product page loaded with high resolution gallery images, several review widgets and a chat script pulling in its own set of fonts is usually the heaviest page on the site, and it is also the one a customer is least willing to wait for.
The e-commerce specific version of this same problem gets a longer treatment elsewhere, covering checkout pages and product variants in more depth. What holds true everywhere is that a checkout page loading review widgets, upsell carousels and a live chat script all at once is competing against its own purpose, since every one of those additions delays the moment a customer can actually pay.
Combining and compressing what you already have
Compression shrinks the size of a file without cutting the number of requests, which makes it the easiest first step because it rarely breaks anything. Text based files, CSS, JavaScript and HTML, compress well because they repeat the same characters and patterns constantly, and a compressed stylesheet is usually a fraction of its original size once it reaches the browser. If you want the underlying mechanics rather than the practical shortcut, the Wikipedia entry on gzip sets out how the compression algorithm actually works.
Combining smaller files into fewer, larger ones cuts the request count directly, though it comes with a trade-off worth naming rather than glossing over: a single large bundle means the whole thing has to finish downloading before any of it can run, where several smaller files can start doing useful work as soon as the first one arrives. Splitting a bundle by page, so the code a product page needs loads separately from the code only the checkout uses, usually beats one giant file loaded everywhere. Work through the deeper walkthrough of the full process if your catalogue is large enough that this summary will not cover every edge case.
Where it is genuinely unclear whether one big bundle or several smaller ones will render faster on your own site, load the product page both ways for a week and watch how long it takes the main image and the add to cart button to appear on a typical mobile connection, not just on the office wifi. A week is usually enough to see a consistent pattern, because the traffic on a product page rarely varies wildly from one day to the next.
Images are usually the biggest single lever
Images are very often the heaviest thing on an e-commerce page and the easiest to fix without touching a line of code, since resizing a photograph to the dimensions it is actually displayed at and choosing a format suited to photographs rather than line art does most of the work on its own. Once product photography enters the mix, the maths changes again, a subject covered in more depth in a piece on how product photography affects this same total.
Lazy loading images that sit below the first screen a customer sees means the browser never fetches them until the customer scrolls that far, which trims the initial request count without removing anything from the page. It does nothing for the gallery images at the top, though, so treat it as a fix for long pages rather than a fix for the heaviest single image on the page.
Caching so the browser stops asking twice
A request that never has to be made again is cheaper than the fastest possible version of the same request. Setting sensible cache headers on images, fonts and any script that rarely changes tells the browser it can reuse the copy it already downloaded on the next visit, rather than asking the server to confirm nothing has changed. Files that do change often, such as a stylesheet updated with every release, need the opposite treatment: a short cache lifetime or a filename that changes when the content does, so a returning customer never sees a stale version of the page.
None of this helps a first time visitor, since caching only pays off on repeat requests to the same file. For a shop where most traffic arrives from search or social rather than returning directly, the earlier changes, compression, combining files and fixing images, matter more than caching ever will, because they help the visitor who has never been to the site before.
Start with whichever page a customer has to get through to buy something, count what it actually loads, and fix the requests doing the least for that page before touching anything else, since reducing HTTP requests is rarely the only lever available, but it is usually the cheapest one to pull first. Compression and combining files are the changes least likely to break something else on the site, which is as good a reason as any to make them the first two changes rather than the last.
Photo by Nick Morrison on Unsplash
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