Query parameters

Real input and output

A query with non-ASCII characters

Input

https://example.com/search?q=developer tools

Output

https://example.com/search?q=developer%20tools

Whole URL versus a single parameter value

Input

https://a.com/b?next=https://c.com/d

Output

encodeURI          https://a.com/b?next=https://c.com/d
encodeURIComponent https%3A%2F%2Fa.com%2Fb%3Fnext%3D...

encodeURI keeps : and / for encoding a full URL. Use encodeURIComponent when the string goes inside one parameter value.

Errors you will hit

You see %2520 or a stray %25

That is double encoding. Encoding an already-encoded string turns % into %25. You need two decode passes, and the cause is usually code that encodes in two places.

A + does not decode to a space

Treating + as a space is a form-encoding rule (application/x-www-form-urlencoded). Plain URL decoding leaves + as a literal plus.

Should slashes be encoded?

Leave / alone when it separates path segments, but encode it as %2F inside a parameter value. This bites most often when passing a redirect URL as a parameter.

Tools that pair well

Common URL encoding mistakes

Know whether you are encoding the whole URL or one value

A full URL and a single query parameter should not always be encoded the same way. Mixing those cases is a common source of broken links.

Double encoding

Encoding an already encoded value can turn spaces into patterns like %2520 and break callback or redirect logic.

Inspect the parsed query table

After encoding or decoding, review the query parameter table so you can confirm the structure instead of trusting the raw string alone.

Where this tool is most useful

Redirect and callback debugging

Helpful for reviewing login redirects, OAuth callbacks, and payment return URLs that carry long parameter chains.

Marketing link QA

It pairs well with the UTM Generator and URL Query Builder when campaign URLs need a final validation pass.

Reproducing API requests

When a request URL is long or full of reserved characters, checking it alongside API Request Tester makes encoding issues easier to isolate.