Parameter value (recommended)
Use encodeURIComponent-style conversion for query values, path fragments, and file names.
URL Encode/Decode (Japanese URL & Query Converter)
Convert URL encode/decode (percent encoding) instantly in your browser. Switch between encodeURIComponent/encodeURI behavior and detect possible double encoding.
Auto mode is the default. Paste input and get immediate output, then copy, swap, or clear in one flow.
Input is processed locally in your browser and is never sent to a server.
How to use
- Paste a URL or parameter string into the input box.
- Choose mode (Auto/Encode/Decode) and target (Parameter Value/Full URL).
- Review the result and copy it. Use Swap when you need another pass.
Which should you choose?
Full URL
Use encodeURI-style conversion when you need to preserve the full URL structure.
+ vs %20
In form-style queries, + may represent a space. You can switch this behavior in Advanced options.
Sample
Japanese URL
Input
https://example.com/検索?q=東京 ランチ&ref=メール#セクション
Output preview
Choose Full URL target to preserve URL structure while converting
UTM parameters
Input
utm_source=メール&utm_campaign=春セール 2026
Output preview
Easy to compare + and %20 behavior
String with symbols
Input
こんにちは/Hello?name=山田太郎¬e=10%OFF
Output preview
Safe decode keeps invalid % sequences and warns instead of crashing
What is URL encode/decode (percent encoding)?
- Percent encoding converts URL-unfriendly characters into %xx form.
- Decoding converts %xx back to original characters.
- It is essential when handling Japanese text, spaces, and symbols in URLs.
When to use encodeURI vs encodeURIComponent
- Use encodeURIComponent behavior for values only (query value or path fragment).
- Use encodeURI behavior for full URLs.
- Choose based on whether delimiters like ? & = / must stay intact.
FAQ
What is the difference between + and %20?
%20 is the RFC-style space representation, while + is mainly used in application/x-www-form-urlencoded conventions. In form-origin queries, + may be treated as a space.
Which function should I use?
Use encodeURIComponent-style conversion for values only, and encodeURI-style conversion for full URLs. Decide based on whether delimiters should remain unchanged.
What is double encoding?
If you see many %25 sequences, the same input may have been encoded multiple times. This tool can detect that and lets you decode once more with one click.