Bencode decoder
Decode bencode — the BitTorrent serialization format behind .torrent files — into readable JSON, or re-encode JSON back into bencode. Runs in your browser; your data never leaves your device.
About this tool
Bencode decoder converts between bencode and JSON in both directions.
Bencode is the compact serialization format used throughout BitTorrent — it
encodes the metainfo inside every .torrent file and the messages exchanged with
trackers and the DHT.
Bencode has just four types:
- Integers —
i42e - Byte strings —
4:spam(a length, a colon, then exactly that many bytes) - Lists —
l4:spami42ee - Dictionaries —
d3:cow3:moo4:spam4:eggse(keys are byte strings, stored in sorted order)
Modes
- Decode parses bencode text into readable JSON.
- Encode serializes JSON back into canonical bencode — dictionary keys are re-sorted by byte value, exactly as the BitTorrent spec requires.
Binary data
A torrent's pieces field is a run of raw 20-byte SHA-1 hashes — not text. Any
byte string that isn't valid UTF-8 is shown as a small sentinel object,
{ "_bencode_bytes_hex": "…" }, holding the bytes as hex. The encoder understands
the same sentinel, so decode then encode reproduces the original bytes exactly.
Notes
Bencode has no boolean or null type, so JSON true/false/null can't be
encoded — use integers (0/1) instead.
Privacy
Everything runs in your browser via WebAssembly — your data is never uploaded to a server. Also available from the gizza CLI and in chat.
FAQ
What is the _bencode_bytes_hex object in my decoded JSON?
It marks a byte string that isn't valid UTF-8 — most commonly a torrent's pieces
field, which is a run of raw 20-byte SHA-1 hashes. The bytes are shown as hex inside
{ "_bencode_bytes_hex": "…" }. The encoder recognizes the same sentinel, so
decoding and re-encoding reproduces the original bytes exactly.
Why do I get "trailing data after top-level bencode value"?
Bencode input must be exactly one top-level value. If anything follows it — a second
value, stray whitespace, or leftover bytes — the decoder rejects it and reports how
many bytes were parsed. The parser is strict in other ways too: i-0e, integers
with leading zeros, and byte-string lengths with leading zeros are all invalid.
Why won't my JSON encode to bencode?
Bencode has only four types: integers, byte strings, lists, and dictionaries. JSON
true, false, and null have no bencode equivalent, so encoding them fails —
replace booleans with 0/1 and drop or substitute nulls first.
Does encoding preserve my dictionary key order?
No — encode mode always emits canonical bencode, with dictionary keys re-sorted by raw byte value, exactly as the BitTorrent spec requires. That's what makes the output suitable for computing a stable info-hash.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool bencode-decoder "d3:cow3:moo4:spam4:eggse"New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/bencode-decoder/?input=d3%3Acow3%3Amoo4%3Aspam4%3Aeggse&mode=decode&pretty=trueMachine-readable descriptor: tool.json — title + parameters JSON Schema for agents.