Feature-rich, API Simulator can be an indispensable tool in your development and testing toolbox. The Standalone API Simulator's features below are not roadmap items - they are available out-of-the-box, right now.
No Coding RequiredConfiguration-driven simulations modelled using simple constructs: name/value pairs, lists, and maps.
Extensible by Scripting
Script anything not built-in yet.
No source code compiling and packaging binaries!
Run API Simulator on local workstations or remote hosts. No need for an application server or external database.
Runs in Docker/OCI containers, including on Kubernetes and OpenShift. Ready-to-use Docker image is available.
ReST, SOAP, RPC style APIs... Using JSON, XML, or a different payload - anything based on HTTP.
TLS Support (HTTPS)
Support for TLS/SSL using X.509 certificate and private key in PEM format, run-time generated self-signed cert, or KeyStore in JKS format.
API Simulator supports HTTP/2 with TLS ALPN, starting HTTP/2 with prior knowledge, and HTTP/2 upgrade from HTTP/1.1
HTTP or HTTPS (!) ProxyOften times it's easier to configure the HTTP client of your application to use API Simulator as HTTP or HTTPS proxy instead of modifying the URLs of simulated API to point to API Simulator.
mTLS (mutual TLS, two-way TLS/SSL)When client authentication is enabled, API Simulator will trust either all client certificates or only those signed by specific CAs.
Comprehensive Request MatchingMulti-value request matching by URI path (route), path pattern, query parameters, HTTP method, header fields, values from the payload, day of the week (no kidding!)...
Multi-response SimletsModel multiple responses in the same simlet configuration without using any scripting.
Request SamplingAdditional request matching in multi-response simlets based on random selection, request sequence number, or fixed rate sampling.
Dynamic ResponsesThe power of responses changing even for the same request using date/time values, computations, parameters from the request, random values, external data stores...
Simula Template Engine
Simula - the flexible templating system developed for API Simulator - drives dynamic response rendering.
Returning static, fixed response for a given request - often times called API mock or stub - is easy with API Simulator.
Stateful API Simulations
API Simulator can maintain state between requests. It is completely dynamic and without a requirement to pre-configure response data.
Simulate Large Content Download
Simulations that stream large content, even bigger than 2GB (!), with only few MB of memory.
Flexible Simlet OrganizationYour choice: single configuration file, a folder structure that suits your needs, or both.
Callbacks over HTTP/1.1 and HTTP/2Built-in support for Request/Acknowledge/Callback message exchanges with async, optionally delayed, callbacks (webhooks).
Default Simulated ResponseDesignate a default response for unrecognized requests. For example, returning "404 Not Found" response with a static or dynamically constructed body.
Forwarding Unrecognized Requests
Unmatched requests can be forwarded to their actual destination and the live responses passed back to the client.
Randomly Generated ValuesTest Data Management via randomly generated numbers, date/time values, tokens from a pattern, random selections from lists...
CSV Data SourcesCSV (comma-separated values) files or embedded in the configuration as source of data to include in dynamic responses.
SQL Data SourcesRelational databases as source of data to include in dynamic responses.
Rate Limiting SimulationsAllow calls at a predefined rate and return an error response (e.g. HTTP "429 Too Many Requests") for calls exceeding the rate.
Latency and Jitter SimulationsAdd delay in sending responses to simulate latency, API slowness, and response time fluctuations for more realistic API simulations. Random, Fixed, Normal or LogNormal distributions.
Connection Dropping SimulationsSimulate unexpected connection closing for a subset of the responses to create chaos and inject faults.
Admin APIs for remote management of API Simulations via calls over HTTP/S secured by a configurable API key.
Declarative ConfigurationDeclarative configuration for customizing and configuring API Simulator and global API Simulation settings.
Simulate Partial ResponsesTo create chaos, simulate partial responses for all or a subset of the requests. How will your API client handle them?
API Simlet EditorOnline API Simlet Editor with suggestions, auto-completion, and more. Now part of API Simulator Cloud. Free!
HTTP API Simulation Fidelity
Support for HTTP protocol-specific features like chunked transfer encoding, compressed output content (gzip, deflate), "keep alive" connections, custom HTTP header fields and methods (e.g. RESET)...
API RecorderCapture raw HTTP traffic and save it into files with API Recorder. Use the recordings to model API simulations.
It gets even better - fully functional API Simulator is free!
There is more, and more is coming. We will gladly look into any suggestions what features to add or how to improve API Simulator.
We invite you to learn more about API Simulator, download it, and run the examples. Why not even create API simulations to help your own testing and development?
Let us know what you think at [feedback at APISimulator.com]. Many thanks for your interest and support!
Happy API Simulating!
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