Protobuf Decoder
Decode Protocol Buffers binary without a schema. Paste hex or base64, or drop a .bin file, and inspect field numbers, wire types and nested messages right in your browser.
How can protobuf be decoded without a .proto schema?
Every protobuf message is a sequence of key-value pairs where the key packs a field number and a wire type. Those two things are embedded in the binary itself, so a raw decoder can walk the bytes and rebuild the structure — field numbers, wire types, nested messages and strings — even without knowing what each field means.
What do the wire types varint, 64-bit, length-delimited and 32-bit mean?
Wire type 0 (varint) is a variable-length integer; 1 (64-bit) is a fixed 8-byte value such as a double or fixed64; 2 (length-delimited) is a length-prefixed blob that can be a string, bytes or a nested message; and 5 (32-bit) is a fixed 4-byte value such as a float or fixed32.
Why does one field show text while another shows a nested message?
Length-delimited fields are ambiguous by design: the same bytes could be a string or a submessage. The decoder first checks whether the bytes are printable UTF-8 text; if not, it tries to parse them as a nested message, and only falls back to a hex preview when neither interpretation fits.
Are negative numbers shown correctly?
Yes. Protobuf stores negative int32/int64 values as 10-byte varints, and the tool shows the unsigned value together with the signed interpretation. sint32/sint64 fields use ZigZag encoding, so small negative numbers appear as small unsigned values in the tree.
Is my data uploaded anywhere?
No. Decoding runs entirely in your browser with JavaScript — the bytes never leave your device. That matters when you are inspecting proprietary or sensitive payloads.
Which input formats are accepted?
Hex text (with or without spaces, colons, commas or 0x prefixes), base64 in standard and URL-safe alphabets, and raw binary files via drag and drop. When a string is ambiguous, hex wins, and you can convert the current input between hex and base64 with one click.
What is this tool useful for?
Reverse engineering undocumented APIs, debugging gRPC services or protobuf-based message queues, inspecting serialized caches and files, learning the wire format, and verifying that your own encoder emits exactly the bytes you expect.
Can it tell me the field names?
No. Field names live in the .proto schema, not in the binary. The tool shows field numbers; once you map a number to a name in your schema you can read the whole tree directly.
What does the byte offset in an error mean?
When the data is corrupted or truncated, decoding stops at the first byte that cannot be parsed. The reported offset points at that exact byte in the input, so you can locate the damage immediately.
How to Use Protobuf Decoder
This protobuf decoder reads raw protocol buffer messages without any .proto schema. Every protobuf payload carries its own field numbers and wire types, so the decoder can rebuild the full message structure — varints, fixed 32/64-bit values, UTF-8 strings and nested submessages — and present it as an expandable tree. Everything runs locally in your browser: your bytes are never uploaded.
- Paste your data into the input box as hex (spaces, colons, commas and 0x prefixes are all fine) or as base64 — the detected format is shown next to the buttons.
- Drop a .bin file onto the input area instead if your payload is raw binary; it is read and decoded immediately.
- Click Demo to load a built-in sample containing a UTF-8 string, zigzag varints, a packed repeated field, a double and a nested message two levels deep.
- Browse the result tree: each row shows the field number, its wire type (varint / 64-bit / length-delimited / 32-bit) and the interpreted value; rows with a caret fold open into nested submessages.
- Use the → Base64 and → HEX buttons to convert the current input between encodings, or Copy HEX to put the equivalent hex string on the clipboard.
- If the data is corrupt or truncated, decoding stops at the first bad byte and the error line tells you the exact byte offset.
When a length-delimited field contains a nested message, it renders as an expandable subtree; if you expected text instead, the bytes simply were not printable UTF-8 — that is how protobuf disambiguation works, not a bug.
Related Tools
- Base64 Encode/Decode Free online Base64 encoder and decoder. Convert text to Base64 and Base64 to text instantly. No server upload, 100% private - runs entirely in your browser.
- Hex Viewer View file contents in hex dump format with search, offset navigation, and virtual scrolling
- Binary to Text Convert binary code to readable text. Decode binary strings (0s and 1s) into ASCII text instantly.
- JWT Decoder Free online JWT decoder. Decode JSON Web Tokens instantly to view header, payload and signature. No registration required.
- X.509 Certificate Decoder Free online X.509 certificate decoder. Paste a PEM or base64 DER certificate to inspect subject, issuer, validity, SANs, key type and fingerprints. 100% local — certificates never leave your browser.
- File Hash Checker Calculate and verify MD5, SHA-1, SHA-256, SHA-512 file hashes locally
- Chmod Calculator Free online chmod calculator to visualize and calculate Linux file permissions with checkboxes. Instantly convert between numeric (755, 644) and symbolic notation (rwxr-xr-x). Supports special permissions like setuid, setgid, sticky bit.
- ASCII Table Complete ASCII character encoding reference with decimal, hexadecimal, octal, binary codes, HTML entities, and character descriptions. Search and filter instantly.