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URL encoding: common mistakes and fixes

Percent-encoding rules for query strings, paths, and plus signs in form data.

2026-05-25 · 4 min read

URLs reserve certain characters. Spaces, ampersands, and Unicode in query values must be percent-encoded. Double-encoding or encoding an entire URL breaks routing and analytics.

Encode per component

Encode the query value hello world as hello%20world, not the full URL. The scheme (https://) and host must remain unencoded.

Plus vs %20

HTML form submissions historically used + for spaces in application/x-www-form-urlencoded bodies. In path segments, %20 is standard. Know which context your framework expects.

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