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A URL looks like one thing.

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It's really a set of instructions, and each part is written for a different reader.

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Take https://www.democompany.com/image.html?size=large#caption.

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The scheme is for the browser.

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https says: speak HTTP, and encrypt it.

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A mailto: scheme would hand the address to your mail program instead.

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The host is for DNS.

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www.democompany.com is looked up and becomes an IP address.

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The port is for the connection.

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Nobody wrote one here, so the browser fills in 443, the default for https.

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The path and the query are for the server.

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They travel inside the request, and the server decides what /image.html and size=large mean.

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To the browser they're just characters.

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Fun fact: the host also travels, in the Host header, so one server can answer for many sites at once.

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And the fragment?

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It never leaves your machine.

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The browser keeps #caption for itself, scrolls to the element with that id, and tells the page's scripts.

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The server never sees it.

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Most links in a page are relative, like the image page's ./assets/media/cat.webp.

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Before any reader sees one, the browser resolves it against the page's own address, borrowing the scheme, the host and part of the path.

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Each reader splits the URL at its own punctuation, so data must not look like punctuation.

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Percent-encoding writes a space as %20 and an ampersand as %26.

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In a form's query string, a plus sign means a space too.

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So when a link breaks, ask which reader it broke for: the browser, DNS, the connection, the server, or the page itself.

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Paste any URL into URL Explorer and see every part, and who reads it.