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RFC 2397 / INLINE DATA URLS

Decode percent escapes as bytes

03

Percent encoding represents one byte with two hexadecimal digits; it is not a Unicode character escape or form-field encoding.

DIAGRAMRead RFC section 3 ↗
RFC 2397 · § 3EXAMPLE
3 / 3
Decode percent escapes as bytesThree percent-decoding cases. The RFC example A percent20 brief percent20 note recovers A brief note. The published original percentbe percentfg percentbe contains non-hex g and is stopped by this teaching decoder. Verified erratum2009 corrects the payload to percentbe percentd3 percentbe, producing octets BE D3 BE; no Greek charset rendering is performed. Erratum2045 separately fixes the grammar import to uric. Percent decoding recovers bytes, not Unicode code points.Percent escapes represent octets%be%d3%beeach %xx → one byteBE D3 BEcharset interpretation is separateVerified correction: %d3 replaces %fg
03
Use the verified corrected bytes.

The corrected %be%d3%be yields BE D3 BE. The diagram stops at octets; it does not claim that each byte is an independent Unicode character.

Source for this drawing: RFC 2397 · Read RFC section 3 ↗

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What changed
RFC2397 §4 original exampleVerified errata2009 and2045

Erratum2009 corrects %fg to %d3. Erratum2045 changes the imported grammar name to uric. Held/reported proposals about parameter quoting are not verified corrections.

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KEY POINT

Recover bytes before interpreting their charset.

  • Without ;base64, safe URL characters represent their ASCII bytes and %xx represents an octet, an eight-bit byte. Hex digits range from 0 to 9 and A to F, case-insensitively.
  • Verified erratum2009 replaces invalid %fg in the Greek-charset example with %d3. The corrected payload %be%d3%be gives bytes BE D3 BE; the declared charset governs any later character interpretation.
  • Verified erratum2045 corrects the imported grammar name from undefined urlchar to uric in RFC2396. Escape characters that would conflict with URL or parameter syntax; do not treat arbitrary raw spaces or quoted strings as safe URL content.
DETAILS

The published A%20brief%20note example yields A brief note. A plus sign is a literal plus byte here, not the space conversion used by some form encodings. The teaching decoder rejects malformed escapes rather than guessing a byte; that error UI is a chosen implementation policy. Errata3214/4124 are Held for Document Update,5923 is Reported and3360 Rejected; none is silently adopted as a verified replacement. The model does not implement a Greek or full MIME charset decoder.

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