Protocol Buffers definitions
Review a self-contained proto3 definition. Compare its structure, formatted source and JSON data shape without changing its field numbers.
Your source stays in this browser. No imports or network requests are made.
Single-file proto3 subset. No imports, custom options, compilation or compatibility checks. Editing source resets the root selection.
Limits: 100,000 UTF-16 characters, 20,000 tokens, 2,000 declarations, 32 levels; 8-second timeout.
Result is out of date. Exports are disabled.
A Protobuf formatter helps when a compact service definition hides the field you need to review. A clean layout alone cannot tell you whether a tag is reserved or a referenced message exists. This workbench checks the supported declarations before making their structure available for export.
Use the tree to distinguish the original field name, its wire number and its resolved type. The JSON Schema view answers a different question: what can the selected message look like as ordinary JSON? Keep the original contract for information that this projection cannot carry.
The Protobuf formatter keeps nested declarations in their original order and displays resolved references with full names. Two messages named Item under different parents remain separate. A recursive link is shown as a reference, so browsing the tree does not expand forever.
Switch the root message to compare the data shapes a consumer will see. Message definitions share $defs rather than being copied into every field. This makes recursive schemas readable and keeps repeated fields, maps and mutually exclusive contact fields visible during review.
The first message is the initial JSON Schema root, including when the file also contains enums and services. Choose another fully qualified message in Options. Editing the source resets this selection so a deleted or renamed root cannot silently remain active.
Expand or collapse declarations without rerunning the checks. A line link returns to that declaration in the source. Long trees reveal 50 visible entries at a time; copying the structure exports the complete declaration list, including collapsed entries.
Automatic checks wait 350 ms after an edit. Turning them off reveals the main button and enables Ctrl/Cmd + Enter. Source or parameter changes immediately disable exports. Example and Clear show a replacement preview; Undo restores both source and result.
Use this proto formatter to normalize indentation to two or four spaces. Tokens inside quoted strings and comments remain intact; fields retain their names, numbers and order. Output is separate from input. The formatted text is parsed again and compared with the original descriptor before it can be exported.
Message tags must be positive, unique within their message and outside 19000–19999. Reserved names and numeric ranges are checked even when their declaration follows the field. Enums must begin with zero; numeric aliases need allow_alias. These checks cover the current file, not its historical contract.
The tree includes package, messages, enums, oneof groups, services and RPC declarations. Field types resolve within the same file, including forward and recursive references. An unresolved type stops output generation. Original snake_case names remain visible even when JSON export uses lowerCamelCase.
The 2020-12 document uses the chosen root and full names in $defs. Repeated fields become arrays, maps become objects and int64 values become strings. Each oneof permits zero or one member, never two. Optional fields remain omittable; this projection does not invent required properties.
No. Message field tags start at 1 and end at 536870911. Tags 19000 through 19999 are also unavailable because the implementation reserves them. This differs from enum values: a proto3 enum must start with a zero-valued declaration. The tool checks the two rules separately rather than applying one number rule everywhere.
Yes. Tags do not need to be consecutive. A message with fields numbered 1 and 20 is valid if neither conflicts with another field or a reservation. Formatting preserves the gap and the declaration order. Use reserved when a removed field number must not be reused; an empty gap alone does not record that history.
Use optional before the field type when you need explicit presence tracking. The tree preserves that distinction. In the exported schema both an ordinary singular field and an optional field may be absent; JSON Schema does not model the generated has-field API or the difference between an unset field and a default value returned by the runtime.
A JSON number handled by JavaScript can lose integer precision beyond its safe range. Common ProtoJSON output therefore represents 64-bit integers as decimal strings. The projection follows this shape without converting the value to Number. Its pattern checks the string shape, so checking the exact signed or unsigned range remains a separate responsibility.
A path is resolved relative to a compiler’s configured import roots, not just the text of the declaration. This workbench has no file tree or dependency resolver and rejects every import explicitly. For a project with dependencies, run protoc or Buf with those files and paths. It will not fetch the path or silently skip the declaration.
Found a definition that should be supported?
Use the Protobuf formatter to inspect the supported structure, then take the source and its reviewed JSON shape back to your project. Final compilation still belongs with the complete dependency set.