Reference

Hosting glossary

73 terms in plain English, with the part that actually matters — not the dictionary definition. Where a term connects to something we have measured or written about, the entry links straight to it.

73 terms · 46 linked to rankings, comparisons or guides

A

Apache: The long-established open-source web server. Flexible and universally supported, but heavier per connection than Nginx or LiteSpeed, which is why most performance-focused stacks put something else in front of it or replace it entirely.
API also: Application Programming Interface: A defined way for one piece of software to talk to another. In hosting it usually means the interface your host exposes for creating servers, clearing caches or pulling metrics without logging into a dashboard.
Auto-scaling: Automatically adding server resources when load rises and removing them when it falls. Useful for genuine traffic spikes; be aware that it converts a performance problem into a billing one, so check whether there is a spending cap.
Availability zone: An isolated data centre within a cloud region, with independent power and networking. Spreading across zones protects you from one building having a bad day — most single-site hosting plans do not do this.

B

Backup: A copy of your files and database you can restore from. The only backup that counts is one you have actually tested restoring — an untested backup is a hypothesis. Check retention (how far back you can go) and whether restores cost extra.; Switching hosts
Bandwidth also: data transfer: The volume of data your site sends to visitors over a period. Rarely a limit for ordinary sites, but automated crawler traffic can consume it invisibly, and "unlimited" bandwidth is always subject to a fair-use clause.; AI crawlers
Bare metal also: dedicated server: A physical server rented entirely to you, with no virtualisation and no neighbours. Maximum control and no contention, at a price and an administrative burden most sites do not need.
Bot traffic: Automated requests from crawlers, scrapers and monitoring tools rather than people. Bots now generate a large share of all web traffic, they consume the same CPU and bandwidth your visitors do, and they never buy anything.; AI crawlers
Brotli: A compression method that shrinks text assets before sending them, typically beating Gzip by 15–20%. Supported by every modern browser; if your host offers it, turn it on and stop thinking about it.

C

Cache: A stored copy of work already done, so it does not have to be repeated. Hosting involves several distinct layers — page cache, object cache, opcode cache, CDN cache — and "caching is enabled" usually means only one of them is.; Host or site?
Cache hit / miss: A hit means the cached copy was used; a miss means the request went through to the origin and did the full work. The gap between your hit and miss response times is the most diagnostic number in web performance.; Host or site?
CDN also: Content Delivery Network: A network of servers worldwide that stores copies of your content and serves the nearest one. It removes distance for cacheable content — and does nothing at all for checkout, admin or any logged-in page.; CDN or faster server? Methodology
Cloud hosting: Hosting on virtualised infrastructure that can be resized on demand, rather than a fixed physical machine. In practice the term is used loosely; what matters is whether resources are genuinely isolated and how quickly you can scale them.; Speed rankings
Core Web Vitals also: LCP, CLS, INP: Google's user-experience metrics: Largest Contentful Paint (loading), Cumulative Layout Shift (visual stability) and Interaction to Next Paint (responsiveness). Your server influences LCP through response time, but the other two are almost entirely about how the page is built.; Host or site?
cPanel: The control panel most shared hosts use for managing files, databases, email and DNS. Ubiquitous and familiar; its licensing costs are also a common reason cited for hosting price rises.; What hosting costs
CPU limit: The processing allowance your plan gets. Exceed it repeatedly and the host throttles or suspends you — including when the load came from bots rather than customers. Check whether your panel reports limit events before assuming your site is at fault.; Host or site? AI crawlers
Cron job: A scheduled task that runs at set intervals — backups, imports, cleanup. WordPress simulates its own version on page loads, which is why a busy site can trigger scheduled work at unhelpful moments.

D

Dedicated server: An entire physical machine for one customer. No noisy neighbours and full control, in exchange for cost and responsibility for the parts a managed host would otherwise handle.
DNS also: Domain Name System: The system that turns a domain name into a server address. When people say a site is 'down' and the server is clearly running, DNS is the usual culprit.; Switching hosts
DNS propagation: The delay between changing a DNS record and every resolver worldwide seeing the change. Governed by your TTL rather than by magic — the folklore figure of 48 hours mostly reflects nobody having lowered the TTL first.; Switching hosts
Downtime: Any period your site is unreachable. Worth measuring from an external monitor rather than trusting a status page, and worth knowing that most uptime guarantees exclude planned maintenance.

E

Edge: The layer of servers closest to your visitors, as opposed to the origin where your site actually lives. "Fast at the edge" and "fast at the origin" are different claims, and marketing pages routinely blur them.; CDN or faster server? Methodology
Entry price vs renewal price: The discounted first-term rate against the standard rate you pay afterwards. Introductory hosting pricing is a loss leader; comparing hosts on it is the single most common buying mistake.; What hosting costs Cloudways vs SiteGround

F

Failover: Automatically switching to standby infrastructure when the primary fails. Common in enterprise plans, rare and usually partial in shared hosting, despite what the marketing implies.
Fair use policy: The clause that defines what "unlimited" actually means. It is where CPU, inode and I/O limits live, and it is the document that determines whether your site gets throttled.; What hosting costs

G

Gzip: The long-standing text compression standard. Still fine, still widely used, and now generally superseded by Brotli where both are available.

H

Headless CMS: A content system that stores and serves content through an API, leaving the front end to something else entirely. WordPress can be run this way. Powerful, and a development project rather than a hosting choice.; Static vs managed WordPress
.htaccess: An Apache configuration file placed in your site directory, commonly used for redirects, caching headers and access rules. Powerful, easy to break, and the first place to look when a migration produces unexpected redirect behaviour.; Switching hosts
HTTP/2 and HTTP/3: Newer versions of the web protocol. HTTP/2 multiplexes many requests over one connection; HTTP/3 moves to QUIC over UDP, which handles unreliable networks better. Both help most on high-latency mobile connections.

I

Inode: A filesystem entry — roughly, one per file or folder. Shared hosts cap them, and sites with large media libraries or heavy caching can hit the limit long before they run out of disk space.
Isolation: How thoroughly your account is separated from others on the same hardware. Strong isolation means a neighbour spike cannot touch you; weak isolation is what produces the noisy-neighbour problem.; Host or site?

J

JAMstack: A way of building sites where pages are pre-built and served as files, with anything dynamic handled by APIs and JavaScript. Fast and cheap to host; every server-side feature you had must be rebuilt as a service.; Static vs managed WordPress

L

Latency: The travel time of a request across the network, before any processing. Largely a function of physical distance, which is why a CDN helps distant visitors and does nothing for local ones.; CDN or faster server?
LCP also: Largest Contentful Paint: How long until the biggest visible element on the page has rendered. Server response time is one input; an oversized hero image is usually a bigger one.; Host or site?
LiteSpeed: A commercial web server with a well-regarded server-level cache (LSCache). Common on performance-oriented shared hosting because caching below PHP is far cheaper than caching inside it.
Load balancer: A component that spreads incoming requests across several servers. Adds capacity and redundancy; adds complexity too, and is rarely relevant below reasonably serious traffic.
Load testing: Measuring how a server behaves with many simultaneous users rather than one. It is where hosts diverge most: a provider that looks quick when idle can degrade sharply under concurrency.; Methodology Speed rankings

M

Managed hosting: A plan where the provider handles server administration, updates, security and backups. You pay more per unit of compute and spend less of your own time — worth it exactly when your time is worth more than the difference.; Comparisons Cloudways vs Kinsta
Migration: Moving a site from one host to another. Does not harm SEO by itself; a badly executed one does. The safe pattern is to build on the new host first and make the switch a single DNS change.; Switching hosts
MySQL / MariaDB: The relational databases most PHP applications run on. MariaDB is a MySQL fork, largely drop-in compatible. Slow queries here are a frequent and often overlooked cause of high server response times.; Host or site?

N

Nameserver: The authoritative server that answers DNS queries for your domain. Pointing your nameservers at a host or a CDN hands them control of your DNS records — convenient, and worth understanding before you do it.; Switching hosts
Nginx: A lightweight, event-driven web server, very efficient at serving static files and handling many concurrent connections. Frequently used as a reverse proxy in front of Apache or PHP-FPM.
Noisy neighbour: Another site on your shared server consuming resources and slowing yours down. You cannot optimise your way out of it, and it is increasingly caused by automated crawler traffic rather than human visitors.; Host or site? AI crawlers
NVMe: A fast solid-state storage interface, considerably quicker than SATA SSDs for the small random reads databases generate. A genuine improvement, though rarely the thing limiting a slow site.

O

Object cache: Stores the results of individual database queries, usually in Redis or Memcached. It speeds up the pages a page cache cannot help with — carts, accounts, admin — which is where slow sites tend to actually hurt.; Host or site?
OPcache: PHP's compiled-bytecode cache, which saves re-parsing your code on every request. It should be on by default; if it is not, enabling it is one of the cheapest performance wins available.
Origin server: The server your site actually runs on, as distinct from any CDN edge in front of it. Origin performance is what we rank on, because it is the only measure that describes the hosting rather than the delivery network.; Speed rankings Methodology
Overselling: Selling more resources than the hardware can deliver, on the assumption that not everyone uses their allocation at once. Standard practice in shared hosting; the degree of it is what separates a good cheap host from a bad one.; What hosting costs

P

Page cache: Stores the finished HTML of a page so subsequent requests skip PHP and the database entirely. The single biggest performance win for content sites, and irrelevant for pages that must be generated per-visitor.; Host or site?
PHP worker: One process able to handle one PHP request at a time. Run out of workers and requests queue, which shows up as sudden slowness under load rather than a steady slowdown.; Host or site?
PHP-FPM: The process manager that runs PHP behind a web server. The number of workers it is allowed determines how many PHP requests can run at once — a common invisible ceiling on busy sites.

R

Rate limiting: Capping how many requests a client may make in a period. The gentler alternative to blocking, and the most practical defence against crawlers that ignore robots.txt.; AI crawlers
Redis: An in-memory data store commonly used for object caching and sessions. Fast, well supported, and often the difference between a tolerable and a genuinely quick WordPress admin.
Renewal pricing: What you pay once the introductory term ends — frequently two or three times the advertised rate. Almost always disclosed at signup, and almost never read. Compare hosts on their three-year total instead.; What hosting costs SiteGround vs Hostinger
Reverse proxy: A server that sits in front of your application, receiving requests and passing them back. Used for caching, TLS termination, load balancing and filtering — Cloudflare is a reverse proxy you rent.
robots.txt: A file at your domain root telling crawlers what they may access. It is a request rather than an enforcement mechanism: well-behaved bots comply, and the ones causing your problems often do not.; AI crawlers

S

Shared hosting: Many sites on one server drawing from a common pool of resources. Cheap and adequate for small sites; its weakness is that your performance depends partly on strangers.; What hosting costs SiteGround vs Hostinger
SLA also: Service Level Agreement: A contractual promise about uptime, and what you get when it is missed. Read the exclusions: planned maintenance is usually exempt, credit is usually capped at a month, and you usually have to claim it yourself.
Soft 404: A page that says "not found" while returning HTTP 200, or a missing URL silently serving other content. Search engines index them as real pages, which is how one site ends up with dozens of duplicates of its own homepage.
SSH also: Secure Shell: Encrypted command-line access to your server. The difference between diagnosing a problem yourself and describing it to support — worth having even if you rarely use it.; Host or site?
SSL / TLS also: HTTPS, certificate: The encryption behind HTTPS. TLS is the current protocol; 'SSL' persists as a habit. Free certificates via Let's Encrypt are standard, so paying for a basic certificate is rarely necessary.
Staging environment: A copy of your site for testing changes before they go live. The single most useful feature on any hosting plan, and the reason agency-focused hosts justify their pricing.; Switching hosts Comparisons
Static hosting also: Cloudflare Pages, Netlify, Vercel: Hosting that serves pre-built files with no application server behind them. Very fast and often free, because the response already exists — and unable to run WordPress, since there is no PHP and no database.; Static vs managed WordPress Speed rankings
Static site generator also: SSG, Astro, Hugo, Eleventy: A tool that turns content and templates into finished HTML at build time rather than per request. The output is plain files, which is what makes static hosting so cheap to serve.; Static vs managed WordPress

T

Throttling: Deliberately slowing an account that exceeds its resource allowance. Often the real explanation for a site that is quick at night and sluggish at midday.; Host or site?
TTFB also: Time to First Byte, server response time: How long the server takes to send the first byte of a response. The clearest single measure of hosting performance, because it captures backend processing before the browser does any work. Under 200ms is good; above 600ms means something is wrong.; Speed rankings Host or site? Methodology
TTL also: Time To Live: How long a cached answer stays valid — most consequentially on DNS records. Lowering your DNS TTL to 300 seconds a day before a migration is what makes a near-zero-downtime switch possible.; Switching hosts

U

Unlimited / unmetered: Marketing language, bounded by a fair use policy. Unlimited storage still has an inode cap; unmetered bandwidth still has a throughput ceiling. Read the clause, not the headline.; What hosting costs
Uptime: The percentage of time a service is reachable. The difference between 99.9% and 99.99% is roughly 43 minutes a month against 4 — which matters enormously to a store and very little to a brochure site.; Speed rankings

V

Varnish: A caching reverse proxy that sits in front of your web server and serves stored responses. Very fast, and awkward with cookies and logged-in traffic, which is why it needs careful configuration on stores.
VPS also: Virtual Private Server: A guaranteed slice of a physical server with its own allocated CPU and memory. The usual step up from shared hosting: real isolation, without the cost of a whole machine.

W

WAF also: Web Application Firewall: A filter between visitors and your site that blocks malicious or abusive requests. Also the most practical place to enforce rules against aggressive crawlers, since it acts before they reach your server.; AI crawlers
Web server: The software that accepts HTTP requests and returns responses — Apache, Nginx, LiteSpeed, Caddy. Distinct from the machine it runs on, though the two are constantly conflated.