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URLEncode

Function URLEncode( const S : String) : String

Example​

procedure ScriptEvent(var Value: variant);
begin
  Value := URLEncode('Customer & Supplier'); // Customer+%26+Supplier
end;

Usage​

URLEncode encodes Unicode text as Velox form-style URL data using UTF-8 percent escapes and plus signs for spaces.

Encoding rules

ASCII letters and digits are retained. Velox also retains these characters unchanged:

* @ . _ - $ ! ' ( )

All other bytes are written as an uppercase %HH escape. Consequences include:

  • space becomes +;
  • a literal plus becomes %2B;
  • %, /, ?, & and = are escaped;
  • ~ is escaped by this legacy safe set even though modern RFC 3986 treats it as unreserved; and
  • non-ASCII characters are first represented correctly as UTF-8 and can therefore produce several %HH sequences.

This safe set and plus-for-space rule make the result suitable for a form/query value convention, not necessarily for every URL component. Encode individual values before assembling the URL; do not encode a complete URL when its structural separators must remain meaningful.

Important behavior and quirks

An embedded #0 terminates processing and silently drops the suffix. Validate inputs if embedded nulls are possible.

Do not encode the same value twice: a percent from the first result is encoded again (%26 becomes %2526). URLDecode is the matching decoding convention.

Additional Technical Info​

URLEncode delegates to Delphi TNetEncoding.URL.Encode. It converts Unicode text to UTF-8 and percent-encodes bytes outside the installed encoder's legacy safe-character set. Ordinary spaces are encoded as +.

The example is fictional and source-reviewed only.

Performance and concurrency

Encoding is linear in the number of input code units plus generated UTF-8 bytes and allocates a new result. It uses no mutable shared state.

Related entries

  • URLDecode - matching form-style decoder.
  • URLEncode2 - ASCII-oriented RFC-3986-like safe set, but not Unicode-safe.
  • URLEncode3 - non-standard Velox legacy safe set, also not Unicode-safe.

External references

Created 2026-07-15