URL Encoder / Decoder

Encode a string for use inside a URL (or decode percent-escapes back to text). Shows component vs full-URI variants and base64url for token use.

Inputs

Any string. UTF-8 bytes are encoded; reserved characters get %XX percent-escapes.

Result

Loading calculator…
—

How to use this calculator

  • Pick a direction.
  • Encode mode: copy whichever variant you need (component / URI / form / base64url).
  • Decode mode: paste any percent-escaped or base64url string and read the original text.

About this calculator

URL percent-encoding is the convention every web framework uses to embed non-URL-safe characters inside a URL. Reserved characters like &, =, ?, /, and space get rewritten as %XX (the hex of the UTF-8 byte). For a path segment or query-string VALUE you almost always want encodeURIComponent — encodeURI is much more permissive and is meant for re-escaping an already-built URL. This tool runs both, plus the form-encoding variant (space→+) and base64url for JWT-style token use.

How it works — the formula

encodeURIComponent: char ∉ [A-Za-z0-9-_.~!*'()] → %XX of UTF-8 byte encodeURI: same, but also excludes reserved URI syntax: / ? # [ ] @ etc. base64url: base64 with +→- /→_ and trailing = stripped

Percent-encoding is byte-level: encode UTF-8 bytes one at a time. A multi-byte character produces multiple %XX sequences. Decoding reassembles the UTF-8 byte stream and re-decodes to a string.

Sources: RFC 3986 — URI Generic Syntax · RFC 4648 — Base16/32/64 Data Encodings · WHATWG URL Standard — Percent-encoded bytes

Worked examples

Example 1
Encode "hello world"
Inputs:
mode=encode, text=hello world
Output:
hello%20world
Example 2
Encode "&=?"
Inputs:
mode=encode, text=&=?
Output:
%26%3D%3F (component) / &=? (URI)
Example 3
Decode "%E4%B8%AD"
Inputs:
mode=decode, text=%E4%B8%AD
Output:
中 (U+4E2D)

Limitations

  • encodeURI vs encodeURIComponent semantics follow WHATWG / RFC 3986 specs.
  • base64url decode is attempted only when input matches the alphabet.
  • No automatic URL parsing — for splitting a full URL into scheme/host/path/query use a URL parser.

Encodings round-trip exactly: decode(encode(x)) === x for any UTF-8 string.

Frequently asked

When should I use encodeURIComponent vs encodeURI?+
encodeURIComponent for any value going into a URL (query-string values, path segments, fragments). encodeURI only for an entire URL where you want to escape stray characters but keep the URL syntax (: / ? = & #) intact.
What is the difference between %20 and + in URLs?+
Both decode to space, but %20 is the universal percent-escape (works anywhere) and + is form-encoding (application/x-www-form-urlencoded). Browsers accept both interchangeably in query strings; servers may not.
What is base64url?+
A URL-safe variant of base64 used in JWT tokens, OAuth, and signed URLs. It replaces + and / with - and _, and drops the trailing = padding.
Why does the decoder fail on some inputs?+
The input contains an invalid %XX sequence — e.g. %ZZ or a trailing % with no hex digits. The tool reports the error rather than guessing.
Does this handle Unicode correctly?+
Yes. encodeURIComponent uses UTF-8 byte sequences; the decode side reassembles them. Emoji and CJK characters round-trip cleanly.

Related calculators

Hex / Binary / Octal / Decimal Converter
Convert numbers between hexadecimal, binary, octal, and decimal. Shows the bit pattern grouped by nibble + the two’s-complement representation for negative values.
ASCII / Unicode Codepoint Lookup
Look up the ASCII/Unicode codepoint for any character — or go the other way and turn a list of codepoints back into text. Shows decimal, hex (U+XXXX), octal, binary, HTML entity, JS escape, and URL-encoded forms for every code point.
Tip Split Calculator
Compute tip and split a restaurant bill evenly among diners.
Fuel vs Electric Car Cost Comparison
Annual fuel cost (gas car) vs annual electricity cost (EV) for the same mileage.
EV Charging Cost Calculator
Cost per session: kWh delivered × $/kWh, accounting for charger efficiency.
Solar Panel Payback Period
System cost / annual savings = years to break even on a residential solar install.

More tools you might like

Hand-picked tools that pair well with this one — same audience, same intent.

ASCII / Unicode Codepoint Lookup
Calc

Look up the ASCII/Unicode codepoint for any character — or go the other way and turn a list of codepoints back into text. Shows decimal, hex (U+XXXX), octal, binary, HTML entity, JS escape, and URL-encoded forms for every code point.

Hex / Binary / Octal / Decimal Converter
Calc

Convert numbers between hexadecimal, binary, octal, and decimal. Shows the bit pattern grouped by nibble + the two’s-complement representation for negative values.

QR Code Payload Formatter (text / URL / WiFi / vCard)
Calc

Build the canonical text payload encoded in a QR code — plain text, URL, WiFi-network credentials, or vCard contact. Includes a ready-to-render image URL for visual scanning.

Freelance Rate Pricing Calculator
Calc

(Target salary + overhead + profit margin) / billable hours = full freelance hourly rate.

Word Count + Reading Time
Calc

Count words, characters, paragraphs, and sentences in any pasted text, plus reading time at 250 / 200 / 150 WPM.

Redact PDF
PDF

Find text and cover it with black rectangles — visual redaction. For full text-stream removal, use a paid pro tool.