Web Development & Performance

The part of the page visible before scrolling. A newspaper term that survived into web design, and still the space where you either earn the scroll or lose the visitor.

In practice On a phone this is roughly one headline, one sentence, and one button. If the visitor cannot tell what you do and how to reach you in that space, the rest of the page is decoration.

A defined way for two pieces of software to exchange information without a human retyping it. When your booking system drops an appointment straight into your calendar, an API did that.

In practice Most “our software doesn’t talk to that” problems are solvable. The real question is whether both vendors expose an API, and what they charge for access to it.

The version of a page you have declared as the official one when the same content is reachable at several addresses. It stops search engines from splitting credit across near-duplicates.

In practice Common on e-commerce sites, where filters and sort orders generate a dozen URLs showing the same products.

A network of servers worldwide that keep copies of your site so every visitor is served from somewhere physically near them. It cuts load times and absorbs traffic spikes without you doing anything.

In practice A visitor in Morehead City hitting a single server in Oregon pays for that distance on every request. A CDN removes the geography from the equation.

Google’s three measurements of real-world page experience: loading (LCP), responsiveness (INP), and visual stability (CLS). Each is graded at the 75th percentile of real visits, split between mobile and desktop — so a page passes only when it is fast for three visitors out of four, not on average.

In practice One fast test on office wi-fi proves nothing. The customer standing on a dock with two bars is inside the measurement, and on a local business site that visitor is often the majority.

How much visible content jumps around unexpectedly while a page loads. 0.1 or less is good; above 0.25 is poor. Movement the visitor caused — opening a menu, expanding an accordion — is excluded.

In practice It is the reason you tap the wrong button when an image loads late. On a booking form or a QR landing page, that mistap is a lost lead outright — and the fix is usually just setting image dimensions.

The internet’s address book, translating your domain name into the numeric address of the server hosting your site. Changing DNS is how a site moves between hosts — and mistakes here take a business offline faster than anything else on this list.

In practice Before any migration, confirm you can log into the registrar yourself. A DNS change you cannot make is a website you do not really control.

A retired responsiveness metric that measured only the delay before the first interaction was handled — not how long the work took, and not any interaction after the first. Google replaced it with INP in 2024.

In practice Treat any audit or proposal still reporting FID as out of date. Nearly every site passed it, which is precisely why it was retired.

Separating where your content is stored and managed from how it is displayed, with the two connected by an API. It buys real flexibility — the same content can feed a website, an app, and a lobby kiosk — at the cost of more moving parts to maintain.

In practice Genuinely useful at a certain size, and overkill for a ten-page brochure site. The question to ask is what second destination the content needs to reach.

How quickly the page visibly responds after someone taps or clicks, measured across the whole visit rather than just the first interaction. 200 milliseconds or less is good; over 500 milliseconds is poor.

In practice It replaced First Input Delay in 2024 and it is much harder to pass. Sites that sailed through the old metric routinely fail this one — nothing changed except that the measurement got honest.

An approach that serves pre-built pages from a CDN and adds dynamic features through APIs, rather than generating every page on a server at request time. In practice it means faster sites with a much smaller attack surface.

In practice The practical benefit for a small business is boring and valuable: fewer things to update, fewer things that can be hacked, and a hosting bill that does not scale with traffic.

How long until the biggest visible element — usually the hero image or headline — finishes rendering. Google considers 2.5 seconds or less good and anything over 4 seconds poor, measured on real visits rather than lab tests.

In practice The usual culprit is a hero photo straight off a phone at 6 MB. Resized to its display size and served as WebP it is often under 200 KB, with no visible difference and seconds off the clock.

Google’s free auditing tool, built into Chrome, that scores a page on performance, accessibility, best practices, and SEO. It runs a simulated load on your own machine, which makes it a useful diagnostic but not the field data Google actually grades you on.

In practice A page can score 98 in Lighthouse and still fail Core Web Vitals, because Google grades real Chrome users on real connections. Use Lighthouse to find the cause, not to declare victory.

Designing the phone layout first and expanding to larger screens, rather than shrinking a desktop design down. Google also indexes the mobile version of your site, so the phone layout is the one that actually gets judged.

In practice For a marine, tourism, or trades business, most visits arrive on a phone, often outdoors in bright sun on a weak signal. That is the design target, not the office monitor it was approved on.

How fast a page becomes usable for a real visitor. It affects both what Google reports about your site and how many people give up before it loads — and on mobile connections those two are tightly linked.

In practice The commercial case is stronger than the ranking case. On a site where a handful of calls a month covers the whole cost, visitors lost to a slow load are measurable in a way rankings never are.

A permanent forward from an old URL to a new one that also passes along most of the old page’s accumulated search credit. Skipping these during a rebuild is the classic way to lose years of rankings overnight.

In practice Every rebuild needs a redirect map made before launch, not after traffic drops. Recovering rankings lost this way takes months; preventing the loss takes an afternoon.

A stylesheet or script the browser must download and process before it can display anything, leaving the visitor on a blank screen. Removing or deferring these is usually the fastest performance win available on an existing site.

In practice Chat widgets, review carousels, and tag managers are the repeat offenders. Each one is a small business decision that quietly costs a fraction of a second on every single page load.

Building one site that reflows to fit any screen size instead of maintaining a separate mobile version. It has been the default approach for over a decade.

In practice If you are being quoted for a separate mobile site in 2026, ask why. You are being sold two things to maintain where one has been standard since roughly 2013.

The most common style of web API, where each piece of data has its own URL and standard web verbs read or change it. It is the default assumption when a vendor says “we have an API.”

In practice Worth confirming rather than assuming. “We have an API” sometimes means a CSV export on a nightly schedule, which is a very different integration.

A file at your domain root telling crawlers which parts of the site they may fetch. It is the one file that major search and AI crawlers consistently honor — including for allowing or blocking AI training bots.

In practice If you want control over how AI companies use your content, this is the file that actually does something. Unlike llms.txt, support for it is universal and deliberate.

A machine-readable list of every page you want search engines to know about, submitted through Search Console. It does not guarantee indexing, but it removes “they never found the page” as an explanation.

In practice Especially worth having on a site with location or service pages that are not all reachable within two clicks of the homepage.

The credential that encrypts traffic between a visitor and your site and puts the padlock in the address bar. Without a valid one, browsers show a “not secure” warning that stops most people cold.

In practice These expire. An expired certificate takes a working site from trustworthy to actively alarming overnight, which is why the renewal wants to be automatic rather than a calendar reminder.

A private copy of your website where changes are built and tested before they reach the public. It is the difference between a broken layout being embarrassing and a broken layout being live on your storefront.

In practice Any vendor editing your live site directly is gambling with the page your customers are on right now. It is a fair question to ask before signing.

Building every page into a finished HTML file ahead of time, so a visitor’s browser downloads a file instead of waiting on a database to assemble one. It is why a well-built brochure site can load almost instantly and almost never go down.

In practice It also removes most of the maintenance surface. There is no database to breach, no plugin stack to patch weekly, and nothing to fall over when you get mentioned somewhere and traffic spikes.

An automatic message one system sends another the moment something happens — a form submitted, a payment cleared, a job marked complete. It is the reverse of an API call: instead of you asking repeatedly, the system tells you.

In practice This is the piece that makes automation feel instant. A review request that goes out the second a job is closed is a webhook doing the work.