The Zdex dump format

In one paragraph

A UTF-8 JSON object: a header (tool, source process, engine guess, engine offsets, globals) and a packages[] array.
Every class, struct and enum has a path such as /Script/Engine.Actor. Paths are the identity; every cross-reference (super class, interfaces, member types, parameter types) is a path.
Sizes and offsets are bytes. A property's size is its total size (element size × array_dim). Addresses are module-relative hex strings.
Unknown keys are ignored, so a dumper can add its own fields. Missing optional keys are fine. Only the keys marked required are required.

Top level

{
  "schema_version": 1,
  "header": {
    "tool_version": "0.3.0",
    "created_utc": "2026-09-15T10:21:04Z",
    "source":  { "kind": "external", "process": "Game-Win64-Shipping.exe", "main_module": "Game-Win64-Shipping.exe",
                 "module_base": "0x7ff64be00000", "image_size": 171896832 },
    "engine":  { "version": "5.6", "confidence": 0.6, "evidence": ["version string: ++UE5+Release-5.6"] },
    "offsets": [ { "name": "UObject.ClassPrivate", "value": 16 }, … ],
    "globals": [ "GObjects=0x98670c0", "FNamePool=0x9783590" ]
  },
  "packages": [
    { "name": "/Script/Engine", "classes": [ … ], "structs": [ … ], "enums": [ … ] }
  ]
}

Key	Required	Meaning
schema_version	yes	Integer, currently `1`. Zdex refuses other values.
header.tool_version	no	Free text naming the dumper and version. Shown on the dump page.
header.created_utc	no	ISO-8601 UTC timestamp of the dump. Becomes the build's "dumped" date.
header.source	no	`kind` is one of `internal`, `external`, `dump`, `static`; `process`, `main_module`, `module_base` (hex string), `image_size` (bytes).
header.engine	no	`version` such as `"5.6"`, `confidence` 0–1, `evidence[]` of human-readable strings.
header.offsets[]	no	Derived engine offsets `{name, value}`, for example `UObject.ClassPrivate`. Negative values mean "not found" and are dropped.
header.globals[]	no	Strings of the form `NAME=0xHEX`, module-relative.
names[]	no	Optional FName pool. Ignored on import.
packages[]	yes	Each with `name` (a package path) and optional `classes[]`, `structs[]`, `enums[]`.

Classes and structs

{
  "name": "Actor", "path": "/Script/Engine.Actor", "cpp_prefix": "A",
  "super": "/Script/CoreUObject.Object",
  "size": 680, "alignment": 8, "inherited_size": 40, "vtable_rva": "0x7d655e8",
  "interfaces": [ "/Script/Engine.Interface_AssetUserData" ],
  "properties": [ … ], "functions": [ … ]
}

Key	Required	Meaning
name, path	yes	Short name and the full object path. The path is the identity across the whole file and across builds.
cpp_prefix	no	`U`, `A`, `F`, `E`, `I`… Used to build the C++ name (`AActor`). Defaults by kind when missing.
super	no	Path of the parent class or struct.
size, alignment, inherited_size	no	Bytes. `inherited_size` is where this type's own members start (aligned).
vtable_rva	no	Classes only, hex string, module-relative.
interfaces[]	no	Paths of implemented interfaces.
properties[], functions[]	no	See below.

Properties

{ "name": "bHidden", "type": { "kind": "bool", "raw": "BoolProperty", "size": 1 },
  "offset": 88, "size": 1, "is_bitfield": true, "bit_index": 7, "byte_mask": 128, "field_mask": 128,
  "flags": 545460846597, "flag_names": ["Edit", "BlueprintVisible", "Net"], "default": "false" }

Key	Required	Meaning
name, type, size	yes	`type` is a type reference (below). `size` is the total size in bytes: element size × `array_dim`.
offset	no	Byte offset inside the owning type. Members without an offset are listed but not placed in the layout.
array_dim	no	Static array element count, only when greater than 1.
is_bitfield, bit_index, byte_mask, field_mask	no	For `bool` bitfields sharing one byte.
flags, flag_names[]	no	Raw EPropertyFlags as an integer and the decoded names.
default	no	Default value as a string, taken from the class default object.

Type references

Recursive. kind is one of bool int8 uint8 int16 uint16 int32 uint32 int64 uint64 float double string name text struct enum objectptr classptr weakptr softptr softclassptr lazyptr interface fieldpath delegate multicast_delegate array set map optional unknown. raw is the engine's property class name (StructProperty). name is the referenced path for struct/enum/object kinds. params[] holds inner types: array and set have one, map has key and value, enum may carry its underlying integer type.

{ "kind": "map", "raw": "MapProperty", "size": 80,
  "params": [ { "kind": "name", "raw": "NameProperty", "size": 8 },
              { "kind": "struct", "raw": "StructProperty", "size": 24, "name": "/Script/CoreUObject.Vector" } ] }

Functions and parameters

{ "name": "SetActorHiddenInGame", "flags": 1409286144, "flag_names": ["Final", "Native", "Public", "BlueprintCallable"],
  "native_rva": "0x1b2c4f0",
  "params": [ { "name": "bNewHidden", "type": { "kind": "bool", "raw": "BoolProperty", "size": 1 }, "size": 1, "offset": 0 } ],
  "script": [ { "offset": 0, "text": "…" } ], "script_size": 42, "script_complete": true }

Key	Required	Meaning
name	yes	Function name inside its class.
native_rva	no	Hex string, module-relative address of the native implementation.
flags, flag_names[]	no	EFunctionFlags raw and decoded.
params[]	no	Each with `name`, `type`, `size`, optional `offset`, `is_out`, `is_const`, `is_return`. There is no separate return field: the parameter with `is_return: true` is the return value.
script[], script_size, script_complete	no	Decompiled Blueprint bytecode as `{offset, text}` lines; `script_complete: false` when decoding stopped early.

Enums

{ "name": "ENetRole", "path": "/Script/Engine.ENetRole", "underlying": "uint8",
  "values": [ { "name": "ENetRole::ROLE_None", "value": 0 }, { "name": "ENetRole::ROLE_Authority", "value": 3 } ] }

underlying defaults to uint8. Values wider than the underlying type are widened on import; negative values in unsigned enums are wrapped.

Rules of thumb for other dumpers

Emit paths exactly as the engine reports them (GetPathName()); Zdex diffs builds by path.
Sizes are bytes, offsets are bytes, addresses are hex strings relative to module_base.
Leave out what you do not know rather than guessing; every key except the ones marked required is optional.
Gzip the file before uploading. The first 64 KB must contain "schema_version" and "header" — write the header first.
Test with the API: POST /upload/init → chunks → finish; a rejected file comes back with a message naming what is missing.

Something in the format holding you back? Say so through the contact form; the schema grows by adding keys, never by breaking existing ones.