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Floci is an open-source tool for running AWS-shaped services locally for development, testing, and CI. Point compatible AWS SDKs, the AWS CLI, Terraform, CDK, OpenTofu, or test suites at http://localhost:4566 instead of a live AWS endpoint. It is an emulator—not an AWS account or proof 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 purpose is to let developers exercise applications and infrastructure workflows on a local machine without connecting to AWS for each development or test run. The project says it is MIT licensed and does not require a cloud account, auth token, or paid feature tier. See the Floci repository for its current documentation and license.
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In practice, tools send AWS-compatible requests to Floci’s local endpoint. That can make it useful for repeatable development and CI, but emulation has boundaries: a listed service does not guarantee every AWS API operation or edge case is implemented. Local success is not a substitute for validating security, permissions, quotas, networking, and production behavior against the AWS environment you intend to use.
How to start Floci
The official documentation presents a CLI route and a Docker Compose route. These are project-provided examples, not independent installation test results. Check the repository for current installation instructions and requirements before using them.
#1 Best Overall
Use the Floci CLI
- Install the CLI using the current instructions on the Floci homepage. The project provides examples for macOS/Linux and PowerShell.
- Start the local services with
floci start. - In a shell, load the environment Floci provides with
eval $(floci env). - Run your AWS CLI commands, SDK-based tests, or infrastructure workflows against the configured local endpoint. The README demonstrates creating an S3 bucket and a DynamoDB table.
Run the Docker image with Compose
The repository’s example uses the floci/floci:latest image and publishes port 4566:
services:
floci:
image: floci/floci:latest
ports:
- "4566:4566"
Configure the client or application with the endpoint, region, and test credentials. The project example uses these shell variables:
AWS_ENDPOINT_URL=http://localhost:4566
AWS_DEFAULT_REGION=us-east-1
AWS_ACCESS_KEY_ID=test
AWS_SECRET_ACCESS_KEY=testFloci’s README says any published AWS region can be used and credentials may be arbitrary nonempty values unless stricter service-specific checks are enabled. Use test credentials only; do not treat them as production credentials. The product page also shows a data bind mount, ./data:/app/data, as a persistence example. Confirm the current documentation for how persistence works with the services and workflows you use.
When your application runs in another container
Inside a separate application container, localhost refers to that application container—not the Floci container. The README warns that service URLs returned with a localhost hostname can therefore point to the wrong place. For Compose-based setups, it documents setting FLOCI_HOSTNAME to the Floci service name. Consult the repository instructions for the current hostname and returned-URL configuration.
Rank #3
Service coverage and compatibility
Floci’s homepage advertises “125 AWS services ready on :4566.” That is the project’s current headline count, not an independently audited inventory or a measure of complete AWS API parity. The README lists services across storage, messaging, databases, identity, compute, analytics, security, and other categories. Before adopting Floci, look up the exact operations your application calls in the project’s service overview.
The README says several services use Docker-backed execution: Lambda, RDS, Neptune, ElastiCache, MSK, ECS, EC2, EKS, OpenSearch, CodeBuild, and Managed Service for Apache Flink. It also describes examples such as S3 versioning and multipart uploads, SQS standard and FIFO queues, DynamoDB indexes and transactions, API Gateway REST and v2, IAM/STS, Cognito, KMS, and Step Functions. These examples indicate documented behavior, not universal support for all operations or exact equivalence to AWS.
A practical compatibility check
- List the specific API operations and event flows your code uses, then verify each against Floci’s current operation-level documentation.
- Check whether any required service uses Docker-backed execution and whether your development or CI environment can run those containers.
- Test the exact SDK, AWS CLI, Terraform, CDK, OpenTofu, or test-suite integration your team relies on.
- Verify resource persistence, returned URLs, and cross-container hostname behavior in your own setup.
- Keep tests against real AWS for behaviors that depend on production IAM, networking, quotas, managed-service integrations, or other cloud-specific conditions.
Floci versus LocalStack: how to assess the choice
Floci’s README says LocalStack’s Community Edition sunset in March 2026 and includes a comparison of authentication requirements, security updates, licensing, performance, and service features. That is Floci’s competitive framing; the reviewed project materials do not independently establish every comparison. Check current primary documentation from both projects before making a decision based on a specific edition, feature, or policy.
Rather than choosing on a headline service count or a broad “drop-in” claim, compare the exact operations and integrations your workload needs, execution model, persistence, setup requirements, and compatibility with your existing tools. A successful migration depends on those details and on testing your own application.
Best Value
Performance figures are project claims
Floci’s homepage reports startup time of 24 ms and idle memory of 13 MiB. Its README also cites an approximately 90 MB Docker image and an approximately 40 MB native binary. The reviewed pages do not describe benchmark hardware, configuration, measurement method, or reproducibility, so treat these as figures published by Floci in 2026 rather than independently verified measurements. The homepage’s 125-service count is likewise a project claim; check operation-level support for your workload.
Who should consider Floci?
Floci is a candidate for developers who want a local AWS-shaped environment for development, automated tests, or CI and whose required services and operations are documented as supported. It is less suitable as the sole validation environment when correctness depends on AWS-specific behavior that the emulator does not reproduce or that has not been verified for the chosen workflow.
The project’s product page and GitHub README are the best places to check current installation details, service coverage, and configuration. Floci’s homepage publishes its headline service and performance claims, which may change over time.
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