Protocol scope and method
Length conventions and framing bytes can differ between profiles. The tool reports actual bytes and both common comparison interpretations.
declaredLength = uint32BE(bytes[0..3]); compare with actual bytes.
Common questions
Does the JT/T 809 Length Validator leave my browser?
No application upload is used. Avoid putting sensitive production data in shareable URLs.
Is this a standards compliance test?
No. Confirm the edition and vendor profile with licensed documents and your target platform.
Offline diagnostic aid. Verify fields, version and vendor extensions before production use.