Links and URLs, in plain language.
Short definitions of the terms you run into when sharing, tracking and redirecting links, each with an example and tools to try.
301 redirect
A 301 redirect is an HTTP response that says a URL has moved permanently. Browsers go to the new address automatically, and search engines treat the new URL as the main one.
Read more →302 redirect
A 302 redirect is an HTTP response that says a URL is temporarily somewhere else. Browsers follow it, but the original address remains the one to use.
Read more →UTM parameters
UTM parameters are short tags added to the end of a URL, such as utm_source and utm_campaign, that tell analytics tools which source, medium and campaign sent a visitor.
Read more →Query string
A query string is the part of a URL after the ? sign. It holds name=value pairs, joined with &, that pass extra information to the page, such as a search term or a filter.
Read more →URL shortener
A URL shortener is a service that turns a long web address into a short one. When someone opens the short link, the service looks up the destination and redirects them to it.
Read more →Open Graph
Open Graph is a set of meta tags in a page's HTML that tell social networks and chat apps which title, description and image to show when the page's link is shared.
Read more →Canonical URL
A canonical URL is the address you tell search engines is the main version of a page, used when the same content can be reached at more than one URL.
Read more →QR code
A QR code is a two-dimensional barcode that stores data, such as a web address, text or Wi-Fi details, in a square pattern that a phone camera can read.
Read more →Dynamic QR code
A dynamic QR code holds a short link instead of the final destination, so where it leads can be changed, and its scans counted, after it has been printed.
Read more →Link rot
Link rot is when a link stops working because the page it pointed to was moved, changed or removed, so that following it ends in an error or the wrong content.
Read more →Redirect chain
A redirect chain is a sequence of two or more redirects between the URL you request and the page you finally reach, such as A to B to C.
Read more →HTTP header
An HTTP header is a name and value sent with every HTTP request or response, carrying information about the message itself, such as its content type, how long to cache it or where to redirect.
Read more →Referrer
The referrer is the address of the page a visitor was on before arriving at yours, sent by the browser in the HTTP Referer header, which analytics tools use to show where traffic comes from.
Read more →URL slug
A URL slug is the part of a web address that identifies a specific page in readable words, usually the last segment of the path, such as spring-sale in example.com/offers/spring-sale.
Read more →Percent-encoding
Percent-encoding, also called URL encoding, replaces characters that aren't allowed in a URL with a percent sign followed by two hexadecimal digits, such as %20 for a space.
Read more →Fragment identifier
A fragment identifier is the part of a URL after the # sign. It points to a place within a page, such as a section or an element, and is handled by the browser rather than sent to the server.
Read more →CNAME record
A CNAME record is a DNS entry that makes one domain name an alias of another, so a lookup for the alias returns the answer for the target name.
Read more →Click-through rate
Click-through rate (CTR) is the percentage of people who click a link, ad or button out of everyone who saw it, calculated as clicks divided by impressions.
Read more →User agent
A user agent is the software that makes a web request on behalf of a person, such as a browser, an app or a search engine crawler, and it identifies itself to servers in the User-Agent header.
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