Browser-only

URL Encode/Decode (Japanese URLs & Query Conversion)

Q: "+ and %20, what’s the difference?"

"“%20” is the RFC-compliant percent-encoding for spaces. “+” is mainly used in HTML forms (application/x-www-form-urlencoded) and is often treated as a space in query strings."

Q: "Which function should I use?"

"For values only (query value, path fragment, file name), choose encodeURIComponent conversion. For whole URLs that must keep ? & = /, choose encodeURI."

Q: "What is double encoding?"

"If %25 (an encoded “%”) appears frequently, the value may be double-encoded. Use “Decode again” to try restoring the original."

URL encode decode (percent-encoding) instantly in your browser. Switch between encodeURIComponent / encodeURI equivalents and detect possible double encoding.

Mode

Target

Advanced options

Input

Output

Idle Conversion runs locally in your browser. No data is sent to a server.

Options

Advanced

Space encoding (when encoding) Choose how spaces are encoded in query-style values. Treat + as space when decoding Common in form and query strings.

Invalid % sequences Malformed or broken percent sequences are preserved or rejected. Newline handling Normalize newlines before encoding or after decoding.

Which one should I use?

Parameter value → encodeURIComponent

Best for query values, path segments, and file names (safe encodeURIComponent conversion).

Full URL → encodeURI

Keeps delimiters like ? & = / so URLs remain readable.

+ vs %20

“%20” is standard. “+” is a form/query convention—toggle it when needed.

Sample inputs

https://example.com/検索?q=東京ランチ&ref=メール#セクション
utm_source=メール&utm_campaign=春セール 2026
こんにちは/Hello?name=山田太郎&note=10%OFF

Shortcuts

Convert now ⌘/Ctrl + Enter

Close warning banner Esc

URL Encode/Decode (percent-encoding)

What is percent-encoding?

URL encode/decode converts non-ASCII and reserved characters into %xx sequences so they can travel safely in URLs.

encodeURI vs encodeURIComponent

Use encodeURIComponent for individual values; use encodeURI for full URLs where delimiters should remain.

Tip

If %25 keeps showing up, the text may be double-encoded. Use the warning banner to decode again safely.

FAQ

+ and %20, what’s the difference?

“%20” is the RFC-compliant percent-encoding for spaces. “+” is mainly used in HTML forms (application/x-www-form-urlencoded) and is often treated as a space in query strings.

Which function should I use?

For values only (query value, path fragment, file name), choose encodeURIComponent conversion. For whole URLs that must keep ? & = /, choose encodeURI.

What is double encoding?

If %25 (an encoded “%”) appears frequently, the value may be double-encoded. Use “Decode again” to try restoring the original.