Understanding URL Structure: Scheme, Host, Path, Query, and Fragment

You almost certainly see strings like "https://waza.tools/tools/url-parser/?lang=en#result" in your browser address bar every day. That is a URL. At first glance it looks like a complicated mix of symbols and letters, but it actually has a well-organized structure in which meaningful parts appear in a fixed order. This article explains what parts a URL is made of and what role each one plays.

What Is a URL

A URL (Uniform Resource Locator) is a string that uniquely points to the "location" of a resource on the web, such as a page, image, or API. Like a postal address used to deliver mail, it expresses in a single line "by which method, on which server, and at which location" to fetch something.

There is also a broader term, URI (Uniform Resource Identifier), but for the everyday "address you can access in a browser," it is fine to think of it as essentially a URL. The URL format is standardized in the RFC 3986 specification, and browsers and servers worldwide interpret it by the same rules. That is exactly why you can reach the same resource no matter which environment you access from.

The easiest way to see how a URL is broken down is to paste a real URL into the URL Parser and watch it split into its individual parts.

URL Structure: Five Parts

A typical URL is broadly made up of the following five parts.

https://example.com:443/path/to/page?key=value#section

Scheme

The scheme is the part at the start of the URL, such as "https," "http," "ftp," or "mailto," and it indicates "by which method to access the resource." It is usually followed by "://." For web pages, https, which encrypts the communication, is the current standard. Unencrypted http can be a security risk depending on the information involved.

Host

The host is the part like "example.com," the domain name that identifies the target server. In actual communication, this domain name is converted to an IP address by DNS, and a connection is made to the corresponding server. A subdomain such as "www." may be prefixed to it.

Port

The port is a number that represents the "connection point" on the server. http defaults to port 80 and https to port 443, and when these standard ports are used, the number is usually omitted. That is why most URLs you see day to day do not show a port number.

Path

The path, like "/path/to/page," indicates which location on the server the resource is at. Similar to a file system folder hierarchy, it expresses levels separated by slashes. Individual pages of a website are, in many cases, distinguished by this path.

The Role of the Query String and Fragment

After the path, you can add two more kinds of supplementary information: the query string and the fragment.

Query string (? and &)

The query string starts with "?" after the path and represents additional parameters passed to the server. The basic form is "key=value," and multiple parameters are joined with "&."

?keyword=url&page=2&sort=new

This example passes three parameters: keyword, page, and sort. It is often used to convey search words, filter conditions, or page numbers, so the same path can produce different results depending on the query. When a value includes non-ASCII characters or symbols, the percent-encoding described below is required.

Fragment (#)

The fragment starts with "#" at the end of the URL and points to a specific position within the page (a heading or element). For example, "#section" scrolls to that spot when the page opens.

An important characteristic of the fragment is that it is not sent to the server and is handled only on the browser side. While the query string is a "condition" passed to the server, the fragment is purely a "position within the page" specified on the client. Keeping this distinction in mind makes the difference easy to organize. The URL Parser lets you confirm such query and fragment extraction at a glance.

How Percent-Encoding Works

A URL has a restriction: only letters, digits, and a few symbols can be used as-is. When you want a value to contain spaces, non-ASCII characters, or symbols that carry special meaning in a URL such as "&," "?," or "#," you need a conversion called percent-encoding (URL encoding).

This works by converting the target characters into bytes and representing each byte as "%" followed by a two-digit hexadecimal number. For example, a space becomes "%20," and the Japanese character "あ" becomes "%E3%81%82" in UTF-8.

• Encoding: converting characters that cannot be used as-is into the "%XX" form.
• Decoding: converting the "%XX" form back into the original characters.

Encoding is essential when placing a search keyword into a query string or generating links correctly. If you forget to encode, an "&" or "#" inside a value can be mistaken for a delimiter, and the URL may not be interpreted as intended. When you want to check whether a string is correctly encoded or decoded, try converting it in the URL Encoder and compare the results. You can see exactly what sequence of "%XX" a string containing non-ASCII characters becomes.

Absolute URLs vs. Relative URLs

URLs come as absolute URLs, which include all parts, and relative URLs, which omit some parts and indicate only the position relative to the current location.

An absolute URL includes everything from the scheme to the path and, on its own, points to the same resource from anywhere in the world. Absolute URLs are required for links to external sites and for URLs shared off-page, such as in email or social media.

A relative URL omits the scheme and host and is interpreted based on "the location of the page you are currently viewing." If it begins with a slash, like "/blog/article," it is a position from the site root; if it begins with "../," like "../article," it points one level up. For links within the same site, relative URLs have the advantage that you do not need to rewrite them even if the domain changes.

Breaking Down a URL in Practice

Everything covered so far sticks much faster once you break down a real URL by hand. Copy one URL from your browser's address bar and try mapping it, from the front, in the order "scheme," "host," "port," "path," "query," and "fragment." The trick is to use the delimiter symbols as markers: what comes before "://" is the scheme, up to the first "/" is the host (and port), up to "?" is the path, up to "#" is the query, and what follows is the fragment.

That said, splitting a long URL with many parameters by hand is tedious. That is where the URL Parser comes in handy. Just paste a URL and it automatically breaks it into parts and lists them, so you can intuitively grasp which symbol marks the boundary of each part. You can also see the query string expanded into its individual keys and values.

In addition, when you want to put a value containing non-ASCII characters or symbols, such as a search keyword, into a query, percent-encode that value with the URL Encoder before embedding it. Comparing the string before and after encoding makes it clear how "あ" becomes "%E3%81%82" and a space becomes "%20." Actually trying both breaking down and converting with your own hands is the fastest path to understanding URL structure.

A URL is a logically structured string in which the parts scheme, host, port, path, query, and fragment appear in a fixed order. Once you grasp the role of each part and how percent-encoding works, many web-related tasks, from creating links and using APIs to tracking down the cause of problems, become much easier.

Please note that this article is intended to provide general information. The details of URL specifications and behavior may differ by environment or implementation, so make your decision after checking the latest official information.