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* Rename `OptimizedMarketOrder` to `OptimizedOrder`
* Create a `OptimizedOrder` subtype `OptimizedNativeOrder`
* Make `quote_simulation_test.ts` type-safer

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Table of contents


The 0x API is a collection of services and endpoints that can be run together or separately. In aggregate, the APIs provide interfaces to 0x liquidity. Everything can be run monolithically via yarn start and docker-compose up as described in Getting Started.


The API contains different services that serve a collection of HTTP or websocket endpoints and keep your order states in sync with the Ethereum state.

HTTP Services

These are services that handle HTTP requests and responses.

Name Path Run Command Requires Ethereum JSON RPC Provider? Requires Relational Database?
All HTTP Services /* yarn start:service:http Yes Yes
Swap /swap yarn start:service:swap_http Yes Yes
Orderbook /orderbook yarn start:service:sra_http No Yes
Meta Transaction Service /meta_transaction yarn start:service:meta_transaction_http Yes Yes

Data Services

The transaction watcher ensures that the data being served is present and up-to-date by keeping the database in sync with Ethereum. The endpoints above run without it, but would be providing degraded or non-functional service.

Name Run Command Requires Ethereum JSON RPC Provider? Requires Relational Database?
Transaction Watcher (monitor and broadcast meta transactions) yarn start:service:transaction_watcher Yes Yes

Getting started



To get a local development version of 0x-api running:

  1. Clone the repo.

  2. Create an .env file and copy the content from the .env_example file. Defaults are defined in config.ts/config.js. The bash environment takes precedence over the .env file. If you run source .env, changes to the .env file will have no effect until you unset the colliding variables.

Environment Variable Default Description
CHAIN_ID Required. No default. The chain id you'd like your API to run on (e.g: 1 -> mainnet, 137 -> Polygon). Defaults to 42 in the API, but required for docker-compose up.
ETHEREUM_RPC_URL Required. No default. The URL used to issue JSON RPC requests. Use http://localhost:8545 to use the local ganache instance.
ZERO_EX_GAS_API_URL Optional. Default: '' The URL used to fetch gas prices. It should be changed to a matching endpoint based on CHAIN_ID.
POSTGRES_URI Required. Default for dev: postgresql://api:api@localhost/api A URI of a running postgres instance. By default, the API will create all necessary tables. A default instance is spun up in docker-compose up
POSTGRES_READ_REPLICA_URIS Optional. No default A comma separated list of URIs of running postgres read replica instances.
FEE_RECIPIENT_ADDRESS 0x0000000000000000000000000000000000000000 The Ethereum address which should be specified as the fee recipient in orders your API accepts.
MAKER_FEE_ASSET_DATA 0x The maker fee token asset data for created 0x orders.
TAKER_FEE_ASSET_DATA 0x The taker fee token asset data for created 0x orders.
MAKER_FEE_UNIT_AMOUNT 0 The flat maker fee amount you'd like to receive for filled orders hosted by you.
TAKER_FEE_UNIT_AMOUNT 0 The flat taker fee amount you'd like to receive for filled orders hosted by you.
WHITELIST_ALL_TOKENS false A boolean determining whether all tokens should be allowed to be posted.
SWAP_IGNORED_ADDRESSES [] A comma separated list of addresses to ignore. These addresses are persisted but not used in any /swap/* endpoints
META_TXN_SUBMIT_WHITELISTED_API_KEYS [] A comma separated list of whitelisted 0x API keys that can use the meta-txn /submit endpoint.
META_TXN_RELAY_PRIVATE_KEYS [] A comma separated list of meta-txn relay sender private keys managed by the TransactionWatcherSignerService.
META_TXN_SIGNING_ENABLED true A boolean determining whether the meta-txn signs and submits transactions .
META_TXN_MAX_GAS_PRICE_GWEI 50 The maximum gas price (in gwei) the meta-txn service will submit a transaction at. If the gas price of the network exceeds this value then the meta-txn service will be disabled.
META_TXN_RELAY_EXPECTED_MINED_SEC Default: 120 The expected time for a meta-txn to be included in a block.
ENABLE_PROMETHEUS_METRICS Default: false A boolean determining whether to enable prometheus monitoring.
PROMETHEUS_PORT Default: 8080 The port from which prometheus metrics should be served.
KAFKA_BROKERS Optional. No default. A comma separated list of Kafka broker servers
KAFKA_TOPIC_QUOTE_REPORT Optional. No default The name of the Kafka topic to publish quote reports on. Setting this and KAFKA_BROKERS enable publishing.
  1. Install the dependencies:

  2. Build the project:

    yarn build
  3. Run docker-compose up to run the other dependencies required for the API. This uses the local docker-compose.yml file.

  4. Run the database migrations:

yarn db:migrate
  1. Start the API

    yarn start

    For development:

    yarn dev

Adding a new contract

NOTE: This repo is undergoing a tooling change.

To add a new contract, you will need to add it to compiler.json.

You can generate the entire list by running the following:

find . -type f -name "*.sol" | grep -v foundry | grep -v "contracts/lib" | grep -v "node_modules"

Developing on Ganache

To use ganache, use the .env file below:


Then run

$ docker-compose up
$ yarn dev

Developing on Foundry

Install Foundry if needed.

Initialize git submodule:

git submodule update --init --recursive

Compile using forge

cd contracts
forge build


Run yarn test. It's really that easy :)

Tip: Test suites set up and teardown sandboxed environments, so using .only on it and describe statements will save lots of development time.


  • yarn build - Build the code
  • yarn test - Test the code
  • yarn lint - Lint the code
  • yarn start - Starts the API
  • yarn dev - Starts the API in dev-mode
  • yarn watch - Watch the source code and rebuild on change
  • yarn prettier - Auto-format the code
  • yarn release - Release a new version of the 0x-api


A Docker image is built and hosted by Dockerhub every time a change to the master branch occurs. A Docker image is built, pushed and tagged when a new version is released as well. Running this image will run 0x API as a monolith, with all its dependencies. You can run any of the services separately by overriding the Docker command with the service-specific command when running the container.

When versioning the API, we freeze the old version in a separate branch so that we can deploy patches, and continue to support the old version until it's officially deprecated. Be aware when contributing fixes that you may want to apply the fix to an older version too.

This is a list of endpoints supported by different versions of the API. If an endpoint is not on this list, it is by default pointed to the master branch.

Endpoint(s) API version branch @0x/asset-swapper branch
/swap/v0/, /meta_transaction/v0
/sra/v3 N/A


Releases are triggered automatically by the release GitHub action. They can also be triggered manually by using yarn release, which requires a GITHUB_TOKEN environment variable.


This project uses TypeORM. It makes it easier for anyone to switch out the backing database used by this project. By default, this project uses a PostgreSQL database.

To add a migration, you may use the following command:

yarn db:migration:create -n myMigration

Legal Disclaimer

The laws and regulations applicable to the use and exchange of digital assets and blockchain-native tokens, including through any software developed using the licensed work created by ZeroEx Intl. as described here (the “Work”), vary by jurisdiction. As set forth in the Apache License, Version 2.0 applicable to the Work, developers are “solely responsible for determining the appropriateness of using or redistributing the Work,” which includes responsibility for ensuring compliance with any such applicable laws and regulations. See the Apache License, Version 2.0 for the specific language governing all applicable permissions and limitations: