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.

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.

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.

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.

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.

Result

Percent-encoded (component)

hello%20world%20%26%20friends

Safe to embed inside a query-string value or path segment.

encodeURIComponent (queries, path segments)hello%20world%20%26%20friends
encodeURI (full URL — keeps :/?&=)hello%20world%20&%20friends
application/x-www-form-urlencoded (form bodies — space→+)hello+world+%26+friends
base64url (JWT / token-safe)aGVsbG8gd29ybGQgJiBmcmllbmRz
UTF-8 bytes21

Source: RFC 3986 §2 — Percent-encoding of URI characters.

Note — Use encodeURIComponent for path segments and query-string values; use encodeURI only for an already-built URL where you want to escape stray characters.

Step-by-step

encodeURIComponent escapes everything except A-Z a-z 0-9 - _ . ~ ! * ' ( ).
encodeURI is more permissive — it keeps reserved syntax characters (: / ? # [ ] @ ! $ & ' ( ) * + , ; =).
Form encoding replaces %20 with + as required by application/x-www-form-urlencoded.

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

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.