URL Encoder & Decoder Online

What is URL encoding?

URL encoding, also called percent-encoding, converts characters that may be unsafe or ambiguous in a URL into a percent sign followed by hexadecimal bytes. For example, a space is usually encoded as %20, a question mark can become %3F, and an ampersand can become %26.

Encoding matters because URLs use some characters as structure. The ? starts a query string, & separates query parameters, = separates keys and values, and # starts a fragment. If those characters are part of your data, encode them so browsers, servers, and APIs read the value correctly.

URL encoding vs URL decoding

Encoding turns readable text into URL-safe text. Decoding reverses the process so an encoded string can be read, checked, or edited. For example, blue%20shoes%20%26%20bags decodes to blue shoes & bags.

Use Encode before placing raw values into query parameters, redirect URLs, tracking links, or API requests. Use Decode when you need to inspect an existing URL, troubleshoot a redirect, or understand a value such as %3F, %2F, or %25.

When should you use encodeURI vs encodeURIComponent?

Use encodeURI for a whole URL when you want to preserve URL syntax characters such as :, /, ?, #, and &. Use encodeURIComponent for a single value, such as a query parameter, path segment, or form value.

In practice, encodeURIComponent is usually the safer choice for user-entered data because it encodes separators that could otherwise change the meaning of the URL.

Full URL:
encodeURI("https://example.com/search?q=blue shoes")

Single query value:
encodeURIComponent("blue shoes & bags")

URL encoding table for common characters

Use this quick reference when checking encoded query strings, redirect URLs, form values, and tracking links.

Reserved vs unreserved URL characters

Reserved characters have special meaning in URLs. Examples include :, /, ?, #, [, ], @, !, $, &, ', (, ), *, +, ,, ;, and =. Encode them when they are data rather than URL structure.

Unreserved characters are generally safe to leave as-is: letters, numbers, hyphen, period, underscore, and tilde (A-Z, a-z, 0-9, -, ., _, ~).

Common URL encoding examples

• %20 means a space in normal percent-encoding.
• + can mean a space in application/x-www-form-urlencoded form data.
• %3F decodes to ?, which normally starts a query string.
• %26 decodes to &, which normally separates query parameters.
• %2520 often means a value was double-encoded, because %25 is an encoded percent sign.

Real-world URL encoding examples

Encoding a query parameter

If a search term contains spaces or symbols, encode the value before adding it to a URL.

Raw value: blue shoes & bags
Encoded: blue%20shoes%20%26%20bags
URL: https://example.com/search?q=blue%20shoes%20%26%20bags

Encoding a redirect URL

Redirect URLs often contain their own query strings, so they should be encoded before being placed inside another URL.

Raw redirect:
https://example.com/callback?token=abc&status=ok

Encoded redirect:
https%3A%2F%2Fexample.com%2Fcallback%3Ftoken%3Dabc%26status%3Dok

Fixing tracking links

Campaign names with spaces, percent signs, ampersands, or non-English characters should be encoded before being used in UTM parameters.

Real-world use cases

• UTM campaign links: Encode campaign names, content labels, and keyword values before adding them to tracking URLs.
• OAuth and SSO redirects: Encode callback URLs before passing them as redirect_uri values.
• Email links: Encode subject lines and body text in mailto: URLs so spaces and symbols survive correctly.
• API requests: Encode user-entered filters, search terms, and IDs before appending them to request URLs.
• Debugging redirects: Decode nested redirect parameters to see where a link is sending users.

Common URL encoding errors

• Encoding a whole URL as a component: This turns https:// into https%3A%2F%2F, which is correct only when the URL is being used as a value inside another URL.
• Double-encoding: Encoding %20 again produces %2520. Decode first if you are not sure whether a value is already encoded.
• Forgetting form mode: Some form-encoded data uses + for spaces. Decode with form mode when inspecting form submissions or legacy query strings.
• Leaving separators inside values: Raw & and = characters can split one value into multiple parameters.

FAQ

What’s the difference between encodeURI and encodeURIComponent?

encodeURI is for whole URLs and leaves URL syntax characters such as :, /, ?, #, and & alone. encodeURIComponent is for individual components like query values and encodes nearly all non-alphanumeric characters.

Why do spaces sometimes appear as + instead of %20?

In application/x-www-form-urlencoded contexts, such as HTML form submissions, spaces are encoded as +. General percent-encoding represents spaces as %20.

Which characters are considered reserved in URLs?

Reserved characters include :, /, ?, #, [, ], @, !, $, &, ', (, ), *, +, ,, ;, and =. These may need encoding when used as data rather than URL separators.

How do I avoid double-encoding?

Only encode raw values once. If you see %25 in output, you may have encoded an already-encoded percent sign. Decode first if unsure, then encode once.

What does %20 mean in a URL?

%20 represents a space character in percent-encoding.

What does %3F mean in a URL?

%3F represents a question mark. It is encoded when the question mark is data, not the start of a query string.

What does %26 mean in a URL?

%26 represents an ampersand. Encoding it prevents the value from being split into another query parameter.

Should I encode a full URL or only the parameter value?

Usually, encode only the parameter value. Encoding an entire URL can turn structural characters like :, /, ?, and & into data.

Why did %20 become %2520?

That usually means the value was encoded twice. The percent sign in %20 was encoded as %25, producing %2520.

Is URL encoding the same as Base64?

No. URL encoding makes text safe inside URLs. Base64 represents binary or text data using a different ASCII format.

References

• RFC 3986: Uniform Resource Identifier (URI): Generic Syntax
• MDN: encodeURIComponent()
• MDN: decodeURIComponent()