Percent-Encoded Query Parameter Name – Decode Spaces and Plus Signs in Keys

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Decode percent escapes in query parameter names and inspect the resulting JSON keys.

24 chars · 1 line

38 chars · 4 lines

2 parameters2 unique keys

Encoded query parameter names

Query parameter names are percent-decoded too

Percent encoding is not limited to values. URLSearchParams also decodes escapes in parameter names, so encoded spaces or plus signs can appear in the JSON keys. This tool is free to use. No account or payment is required.

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What you can do here

  • Browser-native URLSearchParams behavior
  • Full URL and raw query parsing
  • Repeated parameter preservation
  • JSON object to query construction
  • Browser-local processing

Steps

  1. Paste the query into Parse to JSON.
  2. Compare raw encoded names with the decoded JSON keys.
  3. Use stable parameter names when spaces or punctuation are not intentionally part of the API contract.

Names and values share form-url-encoded decoding rules

URLSearchParams decodes each parameter name and value after splitting the query into pairs.

That means %20 becomes a space and %2B becomes a literal plus sign in keys just as they do in values.

Encoded space and plus sign in keys

Both parameter names are decoded before becoming JSON keys.

Query string

?user%20name=Ada&x%2By=1

Parsed JSON

{
  "user name": "Ada",
  "x+y": "1"
}

Common questions

Frequently asked questions

Can a query parameter name contain spaces?

It can after percent decoding, although many APIs choose simpler key names.

Does + in a key become a space too?

A raw + follows form-style space decoding; use %2B for a literal plus sign.

Are encoded names case-sensitive after decoding?

Query parameter names remain ordinary strings; whether an application treats them case-sensitively depends on that application.

Recommended next steps

Percent-Encoded Unicode Query ValueDecode UTF-8 percent escapes such as check marks and CJK text in query parameters.URL Encoder & Decoder OnlineEncode or decode one URL component when percent escapes are the issue.Query String Parser & Builder OnlineParse a URL or raw query into JSON, or build query parameters from JSON.

Debugging a specific Query String issue? Browse Query String troubleshooting.