Serialization

Cap'n Proto Decoder — Segment Dump

Parse Cap'n Proto segment tables (first word = segment count − 1), list segment sizes, dump leading words as hex, and classify the root pointer.

Privacy: Decoding runs entirely in this tab. Your bytes and optional schema text are not uploaded to Codeground servers.

Binary payload

Decoded output

{
  "format": "capnp-segments",
  "segmentCount": 1,
  "segmentSizesWords": [
    2
  ],
  "bytesConsumed": 32,
  "segments": [
    {
      "index": 0,
      "sizeWords": 2,
      "sizeBytes": 16,
      "firstWordsHex": [
        "0000000001000000",
        "2a00000000000000"
      ],
      "rootPointer": {
        "kind": "struct",
        "offsetWords": 0,
        "dataWords": 1,
        "pointerWords": 0,
        "rawHex": "0000000001000000"
      }
    }
  ]
}

Online Cap'n Proto segment dump

Cap'n Proto messages begin with a segment table. This inspector surfaces segment counts, sizes, and root pointer kinds (struct/list/far/null) for quick wire debugging.

Supported input formats

Paste Base64, hex, or PEM (for ASN.1). Auto-detect treats even-length hex strings as hex; otherwise Base64 is assumed. Whitespace is stripped automatically.

Cap'n Proto Decoder FAQ

Do you upload my binary payloads? No. Decoding runs entirely in your browser. Bytes and optional schemas never leave this tab.

Do I need a .capnp schema? Not for segment dumps. Schema-aware field names need the Cap'n Proto toolchain; this tool focuses on framing.

Packed encoding? Paste unpacked stream framing (segment table + segments). Packed packing is not expanded here.

What input formats work? Base64 or hex Cap'n Proto messages.

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