Question 1

Unreserved Characters

Accepted Answer

are those that are inherently safe to use in a URL without any encoding. According to modern standards, this group includes uppercase letters (A-Z), lowercase letters (a-z), digits (0-9), and exactly four special characters: the hyphen (-), period (.), underscore (_), and tilde (~). These characters never need to be percent-encoded. Reserved Characters, on the other hand, are characters that have a special structural meaning within the URL syntax. This group includes characters like the question mark (?) which denotes the start of a query string, the ampersand (&) which separates query parameters, the equals sign (=) which separates a parameter key from its value, and the forward slash (/) which separates directory paths. If you need to use a reserved character for its literal data value—for instance, if a company's name is "Smith & Sons"—it must be percent-encoded (as Smith%20%26%20Sons) so the browser does not mistakenly interpret the ampersand as the start of a new query parameter. Finally, Percent-Encoding is the actual mechanical process of replacing an unsafe character with a % followed by its two-digit hexadecimal equivalent.

Question 2

URL Encoding vs. Base64 Encoding

Accepted Answer

: 
Base64 is designed to take raw binary data (like an image file or a compiled PDF) and convert it into a safe string of ASCII characters. It uses an alphabet of 64 characters (A-Z, a-z, 0-9, +, and /). While URL encoding expands data significantly (up to 300% for non-ASCII characters), Base64 has a fixed overhead, expanding data by exactly 33%. However, Base64 output natively includes the + and / characters, which are reserved in URLs. Therefore, if you need to pass binary data through a URL, you cannot simply use Base64; you must use a variant called "Base64URL" (which swaps + for - and / for _), or you must Base64-encode the data and then URL-encode the resulting string. URL encoding is optimal for small snippets of text and query parameters, while Base64 is strictly for binary data payloads.

Question 3

URL Encoding vs. HTML Entity Encoding

Accepted Answer

: HTML Entity encoding solves a similar problem but for a completely different context. In HTML, characters like < and > are reserved because they define HTML tags. If a user inputs

Question 4

What is the difference between URI, URL, and URN?

Accepted Answer

A Uniform Resource Identifier (URI) is the overarching category for any string that identifies a resource. A Uniform Resource Locator (URL) is a specific type of URI that identifies a resource by providing its exact location and the protocol used to access it (e.g., https://example.com/file.pdf). A Uniform Resource Name (URN) is another type of URI that identifies a resource by name in a specific namespace, regardless of where it is located (e.g., an ISBN number for a book like urn:isbn:0451450523). All URLs are URIs, but not all URIs are URLs. URL encoding technically applies to all URIs.

Question 5

Why do some spaces appear as %20 and others as +?

Accepted Answer

This discrepancy stems from historical contexts. In standard URI percent-encoding (defined by RFC 3986), a space character is always encoded as %20. However, when HTML forms were invented, the W3C decided that spaces in form data submitted via GET or POST requests (using the application/x-www-form-urlencoded MIME type) should be encoded as a plus sign (+). Therefore, if a space is part of a file path (e.g., /my folder/), it must be %20. If it is part of a search query submitted by a form (e.g., ?query=my+search), it is typically represented as a +.

Question 6

Can URL encoding hide data or provide security?

Accepted Answer

Absolutely not. URL encoding is a data translation mechanism, not an encryption algorithm. It provides zero cryptographic security, confidentiality, or data masking. Anyone who intercepts a URL-encoded string can instantly decode it using freely available tools or standard programming libraries. If you need to transmit sensitive information such as passwords, API keys, or personal identifying information (PII), you must rely on transport-layer encryption (HTTPS/TLS) and place the sensitive data in the body of a POST request, rather than exposing it in the URL.

Question 7

What happens if I forget to encode a URL?

Accepted Answer

If you fail to encode a URL containing reserved or unsafe characters, the results are unpredictable but generally catastrophic for the request. The web server, proxy, or browser parsing the URL may misinterpret the structural boundaries of the address. For example, an unencoded ampersand (&) in a data value will be interpreted as the start of a new query parameter, truncating your data. Unencoded spaces may cause the HTTP request to be completely malformed, resulting in the server rejecting the connection entirely with a 400 Bad Request error.

Question 8

Is URL encoding case-sensitive?

Accepted Answer

The percent-encoding process itself specifies that the hexadecimal letters should ideally be uppercase. For example, the space character should be encoded as %20, and a colon should be %3A. However, the RFC 3986 standard explicitly dictates that decoders must be case-insensitive. A properly functioning web server will decode %3A and %3a identically. That said, the unencoded parts of the URL (specifically the directory path) are generally case-sensitive depending on the underlying server operating system (e.g., Linux servers treat /Images/ and /images/ as two different directories).

Question 9

How do I handle emojis in URLs?

Accepted Answer

Emojis are fully supported in modern URLs, provided they are properly encoded using UTF-8. Because emojis exist outside the basic ASCII range, they require multiple bytes to represent. For example, the "thumbs up" emoji (👍) corresponds to the Unicode code point U+1F44D. In UTF-8, this is represented by four bytes: F0 9F 91 8D. When URL-encoded, each byte is individually percent-encoded, resulting in %F0%9F%91%8D. Modern programming languages handle this multi-byte conversion automatically when using standard URL encoding functions like JavaScript's encodeURIComponent().

URL Encoder & Decoder

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