StreamingFast Substreams manifests reference
Tip: When writing and checking your substreams.yaml file, it may help to check your manifest against our JSON schema to ensure there are no problems. JSON schemas can be used in Jetbrains and VSCode. Our manifest schema can be seen here.

Manifests overview

The manifest is the high-level outline for a Substreams module. The manifest file is used for defining properties specific to the current Substreams module and identifying the dependencies between the inputs and outputs of modules.
This reference documentation provides a guide for all fields and values used in a Substreams manifest.


Excerpt pulled from the example Substreams manifest.
manifest excerpt
specVersion: v0.1.0
Use v0.1.0 for the specVersion field.


Excerpt pulled from the example Substreams manifest.
manifest excerpt
name: module_name_for_project
version: v0.5.0
doc: |
Documentation heading for the package.
More detailed documentation for the package.

The field is used to identify the package.
The field infers the filename when the pack command is run by using substreams.yaml as a flag for the Substreams package.
The content of the name field must match the regular expression: ^([a-zA-Z][a-zA-Z0-9_]{0,63})$
The regular expression ruleset translates to the following:
  • 64 characters maximum
  • Separate words by using _
  • Starts by using a-z or A-Z and can contain numbers thereafter


The package.version field identifies the package for the Substreams module.
Note: Thepackage.version must respect Semantic Versioning, version 2.0


The package.url field identifies and helps users discover the source of the Substreams package.


The package.doc field is the documentation string of the package. The first line is a short description and longer documentation proceeds a blank line.


The imports section references WASM code, compiled protobuf definitions, and module definitions.
Tip: Imported modules can be referred to later in the modules section of the manifest through the use of a key.
ethereum: substreams-ethereum-v1.0.0.spkg
tokens: ../eth-token/substreams.yaml
prices: ../eth-token/substreams.yaml
The value is a pointer to a Substreams manifest or a Substreams package.
The filename can be absolute or relative or a remote path prefixed by http:// or https://.
Imports differ across different blockchains. For example, Ethereum-based Substreams modules reference the matching spkg file created for the Ethereum blockchain. Solana, and other blockchains, reference a different spkg or resources specific to the chosen chain.


The protobuf section points to the Google Protocol Buffer (protobuf) definitions used by the Rust modules in the Substreams module.
- google/protobuf/timestamp.proto
- pcs/v1/pcs.proto
- pcs/v1/database.proto
- ./proto
- ../../external-proto
The Substreams packager loads files in any of the listed importPaths.
Note: The imports section of the manifest also affects which .proto files are used in the final Substreams package.
Protobufs and modules are packaged together to help Substreams clients decode the incoming streams. Protobufs are not sent to the Substreams server in network requests.
Learn more about Google Protocol Buffers in the official documentation provided by Google.


The binaries field specifies the WASM binary code to use when executing modules.
The modules[].binary field uses a default value of default.
type: wasm/rust-v1
file: ./target/wasm32-unknown-unknown/release/my_package.wasm
type: wasm/rust-v1
file: ./snapshot_of_my_package.wasm
Important: Defining the default binary is required when creating a Substreams manifest.
See the binary field under modules to see its use.


The type of code and implied virtual machine for execution. There is only one virtual machine available that uses a value of: wasm/rust-v1.


The binaries[name].file field references a locally compiled WASM module. Paths for the binaries[name].file field are absolute or relative to the manifest's directory. The standard location of the compiled WASM module is the root directory of the Substreams module.
Tip: The WASM file referenced by the binary field is picked up and packaged into an .spkg when invoking the pack and run commands through the substreams CLI.


This example shows one map module, named events_extractor and one store module, named totals :
- name: events_extractor
kind: map
initialBlock: 5000000
binary: default # Implicit
- source: sf.ethereum.type.v2.Block
- store: myimport:prices
type: proto:my.types.v1.Events
- name: totals
kind: store
updatePolicy: add
valueType: int64
- source: sf.ethereum.type.v2.Block
- map: events_extractor

Module name

The identifier for the module, prefixed by a letter, followed by a maximum of 64 characters of [a-zA-Z0-9_]. The same rules applied to the field applies to the module name.
The module name is the reference identifier used on the command line for the substreams run command. The module name is also used in the inputs defined in the Substreams manifest.
The module name also corresponds to the name of the Rust function invoked on the compiled WASM code upon execution. The module name is the same #[substreams::handlers::map] as defined in the Rust code. Maps and stores both work in the same fashion.
Important: When importing another package, all module names are prefixed by the package's name and a colon. Prefixing ensures there are no name clashes across multiple imported packages and almost any name can be safely used for a module name.

Module initialBlock

The initial block for the module is where Substreams begins processing data for a module. The runtime never processes blocks prior to the one for any given module.
If all the inputs have the same initialBlock, the field can be omitted and its value is inferred by its dependent inputs.
initialBlock becomes mandatory when inputs have different values.

Module kind

There are two module types for modules[].kind:
  • map
  • store

Module updatePolicy

Specifies the merge strategy for two contiguous partial stores produced by parallelized operations.
The values for modules[].updatePolicy are defined using specific rules stating:
  • set, the last key wins the merge strategy
  • set_if_not_exists, the first key wins the merge strategy
  • append, concatenates two keys' values
  • add, sum the two keys' values
  • min, min between two keys' values
  • max, max between two keys' values

Module valueType

Tip: The module updatePolicy field is only available for modules of kind: store.
Specifies the data type of all keys in the store, and determines what WASM imports are available to the module and are able to write to the store.
The values for modules[].valueTypes can use various types including:
  • bigfloat
  • bigint
  • int64
  • bytes
  • string
Tip: The module valueType field is only available for modules of kind: store.

Module binary

An identifier referring to the binaries section of the Substreams manifest.
The modules[].binary field overrides which binary is used from the binaries declaration section. This means multiple WASM files can be bundled in the Package.
name: hello
binary: other
The default value for binary is default. Therefore, a default binary must be defined under binaries.

Module inputs

- params: string
- source: sf.ethereum.type.v2.Block
- store: my_store
mode: deltas
- store: my_store # defaults to mode: get
- map: my_map
The inputs field is a list of input structures. One of three keys is required for every object.
The key types for inputs include:
  • source
  • store, used to define mode keys
  • map
  • params
You can find more details about inputs in the Developer Guide's section about Modules.

Module output

type: proto:eth.erc721.v1.Transfers
The value for type is always prefixed using proto: followed by a definition specified in the protobuf definitions, and referenced in the protobuf section of the Substreams manifest.
Tip: The module output field is only available for modules of kind: map.


The params mapping changes the default values for modules' parameterizable inputs.
module_name: "default value"
"imported:module": "overridden value"
You can override those values with the -p parameter of substreams run.
When rolling out your consuming code -- in this example, Python -- you can use something like:
my_mod = [mod for mod in pkg.modules.modules if == "store_pools"][0]
my_mod.inputs[0].params.value = "myvalue"
which would be inserted just before starting the stream.