%3B is the URL-encoded semicolon (;).
In a URL, %3B stands for the semicolon (;). Here is when to encode it, what it does in each part of a URL, and what every major language outputs.
Quick facts
| Character | ; |
|---|---|
| Name | Semicolon |
| Unicode | U+003B |
| UTF-8 bytes | 3B (1 byte) |
| Percent-encoded | %3B |
| Lowercase form | %3b — identical meaning |
| Double-encoded | %253B |
| HTML form encoding | %3B |
| RFC 3986 class | Reserved — sub-delimiter |
What it means in a URL
The semicolon is a sub-delimiter. Some servers treat it as a parameter separator (Java servlet ;jsessionid= path parameters, and older query parsers), so encode it as %3B when it is data. Go’s PathEscape encodes it; encodeURI doesn’t.
RFC 3986 class: Reserved — sub-delimiter. RFC 3986 allows it raw in paths and queries, but some schemes and servers give it meaning, so encoding it as data is the safe choice.
When to encode it
| Where it appears | What to do |
|---|---|
| Path segment | Allowed raw (encoding is also fine) |
| Query value | Encode — some servers split on ; |
| Fragment | Allowed raw |
| Form body | Encode |
The mistake to watch for
Values cut off at a raw ; by a framework that still splits query strings on semicolons as well as ampersands.
What each language produces
Left as-is by JavaScript encodeURI(s); every other function in the table encodes it. Output for the single character, UTF-8 input, tested against the real runtimes (see the encoding comparator for your own strings).
| Function | Output | |
|---|---|---|
| JavaScript encodeURIComponent(s) | %3B | encoded |
| JavaScript encodeURI(s) | ; | kept |
| JavaScript URLSearchParams | %3B | encoded |
| Python urllib.parse.quote(s) | %3B | encoded |
| Python quote(s, safe="") | %3B | encoded |
| Python urllib.parse.quote_plus(s) | %3B | encoded |
| PHP rawurlencode($s) | %3B | encoded |
| PHP urlencode($s) | %3B | encoded |
| Java URLEncoder.encode(s, UTF_8) | %3B | encoded |
| Go url.QueryEscape(s) | %3B | encoded |
| Go url.PathEscape(s) | %3B | encoded |
| Ruby URI.encode_www_form_component(s) | %3B | encoded |
| Ruby ERB::Util.url_encode(s) | %3B | encoded |
| C# / .NET Uri.EscapeDataString(s) | %3B | encoded |
Decoding it
decodeURIComponent('%3B') returns the semicolon (;). Python: urllib.parse.unquote('%3B'); PHP: rawurldecode('%3B'). Paste any string into the URL decoder to decode it in your browser.
← %3A Colon · Full URL encoding table · %3C Less-than sign →
Common questions.
%3B is the percent-encoded form of the semicolon (;), whose byte value is 0x3B. Decoding the URL turns it back into the character.
Yes. Hex digits in percent-encoding are case-insensitive, so %3b and %3B mean the same thing. RFC 3986 recommends uppercase, and mixing cases can make caches and analytics count one URL as two.
Use your language’s encoder on the value: encodeURIComponent in JavaScript gives %3B, Python’s quote(s, safe="") gives %3B, PHP’s rawurlencode gives %3B.
More from the toolkit.
About this page. Written and maintained by Sri Murugan Systems, the developer of urlencodedecode.com. Character classes follow RFC 3986 §2; language outputs were generated by running each function in its real runtime.