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Floci is an open-source emulator that lets developers run AWS-shaped services locally for development, testing, and CI. You point compatible AWS tools at http://localhost:4566 instead of an AWS endpoint. It can be a LocalStack alternative for workloads whose required operations Floci supports, but it is not AWS and does not prove that an application will behave identically in production.
What Floci does—and what it does not
Floci describes itself as a free, open-source local AWS emulator. Its official README says standard AWS SDKs, the AWS CLI, Terraform, CDK, OpenTofu, and test suites can be directed to its local endpoint. That lets teams exercise application code and infrastructure workflows without making each development or test request to AWS.
Floci is not an AWS account, and local success is not a substitute for testing in AWS. An emulator can implement the service operations an application needs without matching every AWS feature, edge case, permission rule, or production integration. Check operation-level compatibility and validate important behavior in the actual AWS environment before relying on it in production.
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The project states that it is MIT licensed and does not require a cloud account, auth token, or paid feature tier. Floci’s homepage advertises “125 AWS services ready on :4566”; treat that as the project’s current headline count, not an independent audit of API coverage. A service appearing in an inventory does not establish support for every operation.
#1 Best Overall
How to start Floci locally
The project documents two main routes: use its CLI on your machine, or run the container with Docker Compose. These are the project’s published examples, not independently tested instructions; consult the current project documentation if commands or image details have changed.
Option 1: Use the Floci CLI
- Install the CLI using the current instructions on the Floci homepage, which provides macOS/Linux and PowerShell examples.
- Start the local services by running
floci start. - In a shell, load the environment values provided by Floci with
eval $(floci env). - Use your usual AWS CLI, SDK, or other compatible tooling against the local endpoint. The README demonstrates creating an S3 bucket and a DynamoDB table.
Option 2: Run the Docker image with Compose
The README’s Compose example uses the floci/floci:latest image and publishes port 4566 on the host. Its sample application environment sets the endpoint to http://localhost:4566, the region to us-east-1, and nonempty test access-key values. The product page also shows a data bind mount, ./data:/app/data, as a persistence example. Refer to the current README for the full Compose configuration and any service-specific requirements.
According to the repository, any published AWS region can be used, and credentials may be arbitrary nonempty values unless stricter service-specific checks are enabled. Use test credentials for local work, not production secrets.
When your application runs in another container
In a Compose setup, localhost inside the application container refers to that container itself, not the Floci container. The README warns that URLs returned by Floci which contain localhost can therefore point to the wrong place. It documents setting FLOCI_HOSTNAME to the Floci service name; consult the current hostname guidance when configuring multi-container workflows.
Rank #3
Which AWS services and behaviors does it cover?
The README’s service list spans common application dependencies such as S3, SQS, SNS, DynamoDB, Lambda, IAM, KMS, Secrets Manager, and SSM, along with eventing, APIs, identity, compute, containers, databases, analytics, messaging, security, and other categories. For a decision, the relevant question is not simply whether a service is listed: verify that the specific API calls and integrations your application uses are supported in the Floci README and service overview.
Floci’s README gives examples of behaviors including S3 versioning and multipart upload; standard and FIFO SQS queues; DynamoDB indexes and transactions; API Gateway REST and v2; IAM and STS; Cognito; KMS; and Step Functions. These examples are not a claim of complete AWS API parity.
Docker-backed execution
The project says that Lambda, RDS, Neptune, ElastiCache, MSK, ECS, EC2, EKS, OpenSearch, CodeBuild, and Managed Service for Apache Flink use Docker-backed execution. That is a project description of its implementation, not independent proof of production-equivalent behavior. Check the documentation and run the workflows your team depends on, including any container networking or integration requirements.
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How to judge whether Floci fits your project
Evaluate it against the workload you need to run locally rather than treating “AWS emulator” or a headline service count as a compatibility guarantee.
Best Value
- Operations: List the AWS API calls your code and infrastructure actually make, then check each in the service documentation.
- Integrations: Exercise the SDK, CLI, infrastructure-as-code tool, and test framework used by your project. Endpoint configuration alone does not confirm that every integration behaves as expected.
- Execution model: Find out whether the services you need use Docker-backed execution and account for the resulting container and networking requirements.
- State and repeatability: Decide how local data should persist or reset between runs; the product page shows a bind mount as a persistence example.
- Production validation: Keep tests in AWS for behavior where service fidelity, permissions, or real cloud integrations matter.
Floci’s published speed and size figures
Floci’s 2026 homepage reports startup time of 24 ms and idle memory use of 13 MiB. Its README also lists an approximately 90 MB Docker image and an approximately 40 MB native binary. The reviewed project pages do not state the hardware, configuration, measurement method, or reproducibility conditions behind these figures, so treat them as Floci-published claims rather than comparable benchmark results.
How Floci frames itself against LocalStack
Floci’s README says LocalStack’s Community Edition sunset in March 2026 and includes a comparison table covering items such as authentication tokens, security updates, licensing, performance, and service features. Those statements are Floci’s competitive framing; the reviewed material does not independently establish every comparison. Check current primary documentation from both projects before making a decision based on editions, licensing, or feature availability.
Floci’s project-authored launch post, dated May 20, 2026, discusses the motivation behind the project; it is the publisher’s perspective, not independent validation. The project’s implementation, service coverage, setup guidance, and comparison claims may change over time.
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