How is a URL colloquially known on the Web?

A URL is colloquially known as an address on the Web.

What is the relationship between a URL and a URI?

A URL is a specific type of Uniform Resource Identifier (URI). While many people use the terms interchangeably, a URL implies the means to access an indicated resource, which is not true of every URI. For example, `http://www.example.com` is a URL, but `www.example.com` alone is not.

What are some common applications or uses for URLs?

URLs are most frequently used to reference web pages via protocols like HTTP and HTTPS. However, they are also utilized for various other applications, including file transfer (FTP), email (mailto), and database access (JDBC).

How do most web browsers typically display a URL?

Most web browsers display the URL of a web page in an address bar located above the displayed content.

Can you provide an example of a typical URL structure?

A typical URL, such as `http://www.example.com/index.html`, consists of a protocol (like `http`), a hostname (like `www.example.com`), and a file name (like `index.html`).

When were Uniform Resource Locators (URLs) first defined?

Uniform Resource Locators were defined in RFC 1738 in 1994.

What existing systems were combined to form the URL format?

The URL format combined the pre-existing system of domain names, established in 1985, with file path syntax, using slashes to separate directories and filenames. Conventions already existed for prefixing server names to file paths, often preceded by a double slash.

What was an earlier proposed name for URLs, and what was the reasoning behind the change?

Early collaborators, including Tim Berners-Lee, initially proposed "Universal Document Identifiers" (UDIs). The term "Universal Resource Locators" was also used in an early draft of the HTML Specification in 1993. Berners-Lee later expressed a preference for "universal" over "uniform" in the expansion of the acronym, suggesting it better reflected the original intent.

What are the main components of the generic URI syntax?

The generic URI syntax consists of five components organized hierarchically: scheme, authority, path, query, and fragment. The structure is represented as: `scheme ":" ["//" authority] path ["?" query,"#" fragment]`.

What is the purpose of the "scheme" component in a URI?

The scheme component, which is always defined and non-empty, is the first part of a URI, followed by a colon. It specifies the protocol or access mechanism to be used for retrieving the resource. Examples include `http`, `https`, `ftp`, and `mailto`.

What are some examples of common URI schemes mentioned in the text?

Common URI schemes mentioned include `http` (Hypertext Transfer Protocol), `https` (HTTP Secure), `ftp` (File Transfer Protocol), `mailto` (for email), `file` (for local files), `data` (for embedding data), and `irc` (Internet Relay Chat).

What does the "authority" component of a URI contain?

The authority component, which is optional and preceded by two slashes (`//`), can contain user information, a host, and an optional port number. Its structure is defined as `[userinfo "@"] host [":" port]`.

What is the "userinfo" subcomponent of the authority?

The userinfo subcomponent, if present and followed by an at symbol (`@`), can include a username and an optional password separated by a colon. However, using the `username:password` format is deprecated for security reasons.

What can the "host" subcomponent of the authority represent?

The host subcomponent can be either a registered name, such as a hostname, or an IP address. IPv4 addresses are typically in dot-decimal notation, while IPv6 addresses must be enclosed in brackets (`[]`).

What is the "port" subcomponent of the authority?

The port subcomponent is optional and, if present, is preceded by a colon (`:`). It consists of decimal digits and specifies the network port to connect to on the host.

What defines the "path" component of a URI?

The path component consists of a sequence of segments separated by slashes (`/`). It is always defined for a URI, though it can be empty. While it can resemble a file system path, it doesn't always imply a direct relation to one. If an authority component is present, the path must start with a slash or be empty.

What is "pathinfo" in the context of HTTP/HTTPS URLs?

In HTTP and HTTPS URIs, the last part of the path, known as "pathinfo," is optional. It can represent logical parts or commands passed to a web server's executable module, often used to select or tailor dynamic content, rather than identifying a physical resource like a file.

What is a "clean URL" and how does it relate to pathinfo?

An HTTP or HTTPS URI that includes a "pathinfo" part but no query part can be referred to as a "clean URL." The final part of a clean URL might be a "slug."

What is the purpose of the "query" component in a URI?

The query component, preceded by a question mark (`?`), contains non-hierarchical data, often in the form of attribute-value pairs. It is used to pass additional information to the resource identified by the URL.

What are the common delimiters used in query strings?

By convention, query strings often use attribute-value pairs separated by delimiters. The most common delimiters are the ampersand (`&`) and, historically or in some contexts, the semicolon (`;`).

What is the "fragment" component of a URI used for?

The fragment component, preceded by a hash symbol (`#`), provides direction to a secondary resource or a specific part of the primary resource. For HTML documents, this is often an element's `id` attribute, causing browsers to scroll to that element.

How does a web browser typically "dereference" a URL?

A web browser typically dereferences a URL by initiating an HTTP request to the specified host. For HTTP URLs, this is usually on port 80, while HTTPS URLs require a secure connection.

What is an Internationalized URL (IRI)?

An Internationalized URL (IRI) is a form of URL that can include Unicode characters, allowing users to create URLs in their own local alphabets and languages. All modern browsers support IRIs.

What are Internationalized Domain Names (IDNs)?

Internationalized Domain Names (IDNs) are the domain name parts of IRIs that use characters from local alphabets. Web software automatically converts these into Punycode for use with the Domain Name System.

How are non-ASCII characters handled in the domain name part of an IRI?

Domain names in IRIs are converted into Punycode, a representation using only ASCII characters, which is compatible with the Domain Name System. The prefix `xn--` indicates that the original characters were not ASCII.

How are non-ASCII characters handled in the path part of an IRI?

If a URL path contains characters not part of the basic URL set, they are converted to UTF-8 and then escaped using percent-encoding (e.g., `%E5%BC%95`). This allows the target computer to decode the address correctly.

What is percent-encoding?

Percent-encoding is a mechanism used to represent characters that are not part of the standard URL character set. Non-ASCII characters in internationalized URLs are converted to UTF-8 and then escaped using percent-encoding, typically appearing as a percent sign followed by two hexadecimal digits.

What are protocol-relative URLs (PRLs)?

Protocol-relative URLs (PRLs), also known as protocol-relative links (PRLs), are URLs that omit the protocol scheme. For example, `//example.com` will automatically use the same protocol (HTTP or HTTPS) as the current page.

Who is credited with the invention of the World Wide Web and the initial definition of URLs?

Tim Berners-Lee is credited with the invention of the World Wide Web and played a key role in the initial definition of URLs.

What is the role of the Internet Engineering Task Force (IETF) concerning URLs?

The IETF, specifically its URI working group, was involved in the definition of Uniform Resource Locators (URLs) in RFC 1738 in 1994. They continue to be involved in standards related to internet protocols and addressing.

What does the "status" field in the infobox indicate for URL?

The status field in the infobox indicates that the URL standard is "Published."

When was the "Living Standard" version of the URL specification last updated, according to the infobox?

The "Living Standard" version of the URL specification was last updated in 2023, according to the infobox.

What organization is currently responsible for the "Living Standard" URL specification?

The Web Hypertext Application Technology Working Group (WHATWG) is responsible for the "Living Standard" URL specification.

What is the purpose of the "fragment identifier" in a URL?

A fragment identifier, indicated by a hash symbol (`#`), provides direction to a secondary resource or a specific section within the primary resource identified by the URL. For example, in an HTML document, it can point to an element with a specific `id` attribute.

What is the significance of RFC 3986 in relation to URLs?

RFC 3986, titled "Uniform Resource Identifier (URI): Generic Syntax," is a foundational document that defines the generic syntax for URIs, which includes URLs. It is considered Internet Standard 66.

What does the term "URL" stand for?

URL stands for Uniform Resource Locator.

What is the primary function of a URL?

The primary function of a URL is to specify the location of a resource on a computer network and provide a mechanism for retrieving it.

What is the difference between a dot-decimal notation and bracketed notation for IP addresses in URLs?

Dot-decimal notation is used for IPv4 addresses (e.g., `192.168.1.1`), while IPv6 addresses are enclosed in brackets (e.g., `[2001:0db8:85a3:0000:0000:8a2e:0370:7334]`).

What does the "scheme" component of a URL define?

The scheme component defines the protocol used to access the resource, such as HTTP for web pages or FTP for file transfers. It is always present and followed by a colon.

What is the "authority" component in a URL syntax?

The authority component, typically appearing after `//`, specifies information about the server or resource location, including the host, and optionally user credentials and a port number.

What is the "path" component's role in a URL?

The path component specifies a particular resource within the server identified by the authority, often resembling a file or directory structure on a file system.

What is the "query" component used for in a URL?

The query component, following a `?`, is used to send additional data to the server, often used in web applications to filter or specify search parameters.

What is the "fragment" component used for in a URL?

The fragment component, following a `#`, refers to a specific section or piece of information within the resource itself, such as a heading or an element on a web page.

What is the purpose of the "host" subcomponent within the authority?

The host subcomponent identifies the specific server or network location where the resource is located, using either a domain name or an IP address.

What is the "port" subcomponent used for?

The port subcomponent specifies a particular communication endpoint on the host server, often used when a service is not running on the default port for its protocol.

What is the difference between a URL and a URN?

While both are types of URIs, a URL (Uniform Resource Locator) specifies *how* to access a resource (its location and access mechanism), whereas a URN (Uniform Resource Name) aims to provide a unique, persistent identifier for a resource, independent of its location.

What does the `mailto:` scheme indicate in a URL?

The `mailto:` scheme indicates that the URL refers to an email address, typically used to initiate an email composition.

What is the function of the `file` scheme in a URL?

The `file` scheme is used in URLs to indicate a resource located on the local file system or accessible via a file transfer protocol.

What is the "latest version" of the URL specification mentioned in the infobox?

The "Living Standard" version of the URL specification is listed as the latest version, updated in 2023.

Url Wiki: The Web's Address System: Decoding Uniform Resource Locators

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What is a URL?

Resource Locator

A Uniform Resource Locator (URL), colloquially known as an address on the Web, is a reference to a resource that specifies its location on a computer network and a mechanism for retrieving it.^[6] It is a specific type of Uniform Resource Identifier (URI), though the terms are often used interchangeably.^[7]^[a]

Ubiquitous Application

URLs are most commonly used to reference web pages via the Hypertext Transfer Protocol (HTTP/HTTPS). However, their application extends to various other protocols and services, including file transfer (FTP), email (mailto), and database access (JDBC), among many others.^[10]

Address Bar Standard

Most web browsers display the URL of the current web page prominently in their address bar. A typical URL structure, such as http://www.example.com/index.html, clearly delineates the protocol (http), the hostname (www.example.com), and the specific resource path (index.html).

Historical Development

Genesis of URLs

The formal definition of Uniform Resource Locators emerged in 1994 within RFC 1738, authored by Tim Berners-Lee, the architect of the World Wide Web, and the URI working group of the Internet Engineering Task Force (IETF).^[11]^[12] This development was a culmination of collaborative efforts initiated at an IETF meeting in 1992.^[12]

Syntactic Evolution

The URL format ingeniously merged the established domain name system (dating back to 1985) with file path conventions, utilizing slashes to delineate directories and filenames.^[13] Early proposals considered "Universal Document Identifiers" (UDIs) and "Universal" Resource Locators, reflecting a desire for a comprehensive naming system, though the term "Uniform" eventually prevailed.^[15] Berners-Lee later expressed a preference for the "universal" designation and noted the redundancy of the double slashes following the scheme.^[14]

URL Syntax Breakdown

Hierarchical Structure

A URL adheres to the generic URI syntax, comprising five hierarchical components, ordered by decreasing significance from left to right:

URI = scheme ":" ["//" authority] path ["?" query] ["#" fragment]

The scheme and path are always defined, while authority, query, and fragment are optional. Components are considered undefined if their delimiter is absent, and empty if they contain no characters (except for the scheme, which must be non-empty).^[1]

Key Components Explained

Let's dissect the primary components:

Scheme: Identifies the protocol (e.g., http, https, ftp, mailto). It begins with a letter and can include letters, digits, '+', '.', or '-'. Schemes are case-insensitive, but lowercase is canonical.^[18]
Authority: Optional component, preceded by //. It includes optional userinfo (username:password, deprecated for security), the host (hostname or IP address), and an optional port number.
Path: A sequence of segments separated by slashes (/), representing the location of the resource. It can resemble a file system path but doesn't always imply a direct mapping.
Query: Optional component, preceded by ?, containing non-hierarchical data, often in attribute-value pairs.
Fragment: Optional component, preceded by #, identifying a specific part of a resource (e.g., a section in an HTML document).

Query Delimiters

The query component often consists of attribute-value pairs. While the syntax is flexible, conventions dictate how these pairs are structured:

Query Delimiter	Example
Ampersand (`&`)	`key1=value1&key2=value2`
Semicolon (`;`)^[c]	`key1=value1;key2=value2`

Historically, RFC 1866 encouraged support for semicolons in addition to ampersands.^[c]

Internationalized URLs

Embracing Global Languages

To accommodate users worldwide, URLs can now include characters from various alphabets. An Internationalized Resource Identifier (IRI) is a URL that supports Unicode characters.^[23]^[24] Modern browsers fully support IRIs.

IDNs and Encoding

The domain name part of an IRI is known as an Internationalized Domain Name (IDN). Web software automatically converts these into Punycode, a format compatible with the Domain Name System (DNS). For example, a Chinese URL might become http://xn--fsqu00a.xn--3lr804guic/.^[25] Similarly, URL path names can use local scripts, which are then encoded using UTF-8 and percent-encoding for characters outside the standard URL set (e.g., Japanese characters becoming %E5%BC%95%E3%81%8D%E5%89%B2%E3%82%8A.html).^[23]

Protocol-Relative URLs

Flexible Linking

Protocol-relative links (PRLs), or protocol-relative URLs (PRURLs), are URLs that omit the protocol scheme. For instance, //example.com will automatically adopt the protocol (typically HTTP or HTTPS) of the current page.^[26]^[27] This offers flexibility, especially when serving content over both HTTP and HTTPS.

Related Concepts

Key Terminology

Understanding URLs involves familiarity with related concepts:

Hyperlink: A reference enabling users to navigate between resources.
URI: A broader term encompassing URLs and URNs (Uniform Resource Names).
URI Fragment: A part of a URL (after '#') that points to a specific section within a resource.
Hostname: The domain name or IP address identifying a server.
URI Scheme: The protocol identifier (e.g., http, ftp).
URL Normalization: The process of transforming a URL into a canonical form.
URL Redirection: Automatically forwarding a user from one URL to another.

Identifier Landscape

URLs exist within a larger framework of resource identification:

Internationalized Resource Identifier (IRI): An IRI is a URL that supports Unicode characters, allowing for non-ASCII characters in domain names and paths.
Persistent Uniform Resource Locator (PURL): A PURL is a type of URL designed to remain stable over time, even if the resource's actual location changes.
Uniform Resource Name (URN): A URN provides a persistent, location-independent identifier for a resource.

Further Exploration

Official Specifications & Tools

For deeper technical understanding and practical application, consult these resources:

URL specification at WHATWG
URL splitter tool

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This page was generated by an Artificial Intelligence and is intended for informational and educational purposes only. The content is based on a snapshot of publicly available data from Wikipedia and may not be entirely accurate, complete, or up-to-date.

This is not professional technical advice. The information provided on this website is not a substitute for professional consultation regarding web development, network protocols, or software architecture. Always refer to official documentation and consult with qualified professionals for specific technical requirements or implementation guidance.

The creators of this page are not responsible for any errors or omissions, or for any actions taken based on the information provided herein.

The Web's Address System

💡 Dive in with Flashcard Learning! 💡

What is a URL? ℹ️

📍 Resource Locator

🌐 Ubiquitous Application

🖥️ Address Bar Standard

Historical Development ⏳

📜 Genesis of URLs

🏗️ Syntactic Evolution

URL Syntax Breakdown ⚙️

📐 Hierarchical Structure

🔑 Key Components Explained

📊 Query Delimiters

Internationalized URLs 🌍

🌐 Embracing Global Languages

🔤 IDNs and Encoding

Protocol-Relative URLs ↔️

🔗 Flexible Linking

Related Concepts 💡

📚 Key Terminology

🔗 Identifier Landscape

Further Exploration 🚀

🔗 Official Specifications & Tools

Teacher's Corner 🧑‍🏫

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📜 Important Notice

Dive in with Flashcard Learning!

What is a URL?

Resource Locator

Ubiquitous Application

Address Bar Standard

Historical Development

Genesis of URLs

Syntactic Evolution

URL Syntax Breakdown

Hierarchical Structure

Key Components Explained

Query Delimiters

Internationalized URLs

Embracing Global Languages

IDNs and Encoding

Protocol-Relative URLs

Flexible Linking

Related Concepts

Key Terminology

Identifier Landscape

Further Exploration

Official Specifications & Tools

Teacher's Corner

True or False?

Test Your Knowledge!

Gamer's Corner

Discover other topics to study!

References

Feedback & Support

Disclaimer

Important Notice