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FIX connectivity to Polymarket US is provisioned via AWS VPC PrivateLink. After your onboarding is complete, you will receive your connection details in the FIX Connectivity form:

Download FIX Connectivity Form

Template form for FIX session configuration and connection details

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AWS VPC Connection Setup

Connecting to Polymarket Exchange FIX services from your AWS VPC involves adding VPC Endpoints to your VPC’s private subnets. You will need to have at least one (preferably 3) subnets in the Availability Zone IDs that are supported by the Polymarket environment you are connecting to.
AWS randomly maps Availability Zones to physical Zone IDs per account. Please verify that the Zone IDs match. Learn more about Availability Zones.

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Supported AWS Availability Zone IDs

EnvironmentZone IDs
Productionuse1-az1, use1-az2, use1-az6
Pre-Productionuse1-az1, use1-az2, use1-az4
We strongly recommend using separate AWS accounts to clearly distinguish between your production and non-production sessions.

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Creating a VPC Endpoint

In your AWS Console, create a new VPC Endpoint using the VPC Service Name provided to you based on the specific environment you want to connect to.

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1. Navigate to the VPC Console

  1. Open the Amazon VPC console in the AWS Management Console
  2. In the navigation pane, choose Endpoints
  3. Choose Create endpoint

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2. Configure the Endpoint Settings

  • (Optional) For Name tag, enter a descriptive name for your endpoint
  • For Service category, select Endpoint services that use NLBs and GWLBs
  • For Service name, enter the exact service name provided to you and choose Verify service
  • For VPC, select the VPC from which you will access the service
  • For IP address type, choose IPv4

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3. Configure Subnets and Security

  • For Subnets, select one subnet per Availability Zone where you want to create an endpoint network interface. For high availability, select at least two AZs
  • For Security Group, select a security group that allows inbound traffic from the resources in your VPC that need to access the service on the required ports

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4. Connection Approval

Once you’ve created the VPC Endpoint, a connection request will be sent to Polymarket. Our DevOps team will review and accept the request, and we will notify you once it has been approved.
You will not be able to proceed with DNS configuration or FIX connection until we’ve accepted the connection on our end.

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5. Enable Private DNS

After connecting to the endpoint, enable Private DNS for the endpoint. When Private DNS is enabled, the DNS names provided to you will resolve to private IP addresses assigned to your VPC Endpoint, and all traffic will route over the private AWS network.

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Retrieving Your VPC Endpoint DNS Name

It is recommended to use the DNS name provided to you and not the AWS-generated DNS names assigned to your VPC Endpoint.
To connect to the VPC Endpoint Service, you can use the AWS-assigned DNS name generated within your account, or the Private DNS described above. If you choose the AWS-assigned DNS name, it will continue to work independent of the Private DNS.

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Option 1: Using the AWS Management Console

  1. Log in to your AWS account and navigate to the VPC Console
  2. In the left navigation pane, select Endpoints
  3. Select the Interface Endpoint you created for this service (search by the Service Name if needed)
  4. In the Details tab at the bottom of the screen, locate the DNS names section
  5. Copy the first entry listed (the Regional DNS Name)
Do not use the zonal DNS names (the ones containing availability zone letters like .us-east-1a.) unless you are specifically targeting a single zone.

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Option 2: Using the AWS CLI

If you have the AWS CLI configured, run the following command to retrieve the DNS names directly: 
aws ec2 describe-vpc-endpoints \
    --filters Name=service-name,Values=[VPC_SERVICE_NAME] \
    --query "VpcEndpoints[0].DnsEntries[*].DnsName" \
    --output text
Replace [VPC_SERVICE_NAME] with the VPC Service name that was provided to you for the initial creation of the VPC Endpoints. You can also run this in CloudShell from the AWS Web Console.

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FIX Session Configuration

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Session Identifiers

Your FIX engine will initiate the TCP connection sessions to Polymarket Exchange using FIXT.1.1 transport with FIX 5.0 SP2 application messages. Identifiers can include ASCII printable characters excluding SOH (Start of Header) characters only. SenderCompID (Tag 49): The firm ID assigned by Polymarket to your firm’s FIX session (e.g., YOURFIRM_PMX_OE, YOURFIRM_PMX_MD, YOURFIRM_PMX_DC) TargetCompID (Tag 56): The exchange ID assigned by Polymarket to your firm’s FIX session (e.g., PMX_YOURFIRM_OE, PMX_YOURFIRM_MD, PMX_YOURFIRM_DC) SenderSubID (Tag 50): The trader identifier assigned based on the user we create at Polymarket (e.g., 20251118-yourfirm-api-user-1), sent on order and order-management messages Account (Tag 1): The account identifier assigned based on the account we create at Polymarket (e.g., 20251118-yourfirm-api-account-1), sent on orders to attribute trading activity

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Session Types

Polymarket Exchange provides three types of FIX sessions:
Session TypePurposePort
Order Entry (OE)Submit and manage ordersProvided in connection details
Market Data (MD)Subscribe to market data feedsProvided in connection details
Drop Copy (DC)Receive execution reportsProvided in connection details

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Sequence Number Reset

Each participant’s FIX session can have a different sequence reset time (e.g., 00:00:00 UTC, 00:00:00 ET). Your configured reset time will be provided in your connection details.

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Testing Your Connection

Once your VPC Endpoint is approved and configured:
  1. Test connectivity to each port (Order Entry, Market Data, Drop Copy)
  2. Initiate FIX sessions using the identifiers provided
  3. Verify sequence number behavior and message flow
  4. Test order submission and market data subscriptions
For detailed FIX protocol specifications, see: