API Simulator 1.5 Release – HTTP/2 Support is Here!

December 30, 2019


We are excited to announce API Simulator version 1.5 and the support for the HTTP/2 (HTTP2) protocol!!! After three release candidates, the official support for HTTP/2 is here.

To our knowledge, API Simulator is the first free API simulation tool to offer HTTP/2 in a stable release – not just some beta or a roadmap item – for running HTTP API simulations.

Moreover, the support for HTTP/2 includes all three ways to start an HTTP/2 connection: TLS with ALPN, prior-knowledge, and upgrade from HTTP/1.1.


Below is a brief recap of the HTTP/2 support in API Simulator as of version 1.5:

  • Auto-detection and negotiation of the HTTP protocol – HTTP/1.x or HTTP/2 – and connection method. No additional startup arguments or switches required!
  • HTTP/1.x and HTTP/2 requests on the same port number.
  • HTTP and HTTPS on the same port number for HTTP/1.x and HTTP/2 requests.
  • Starting HTTP/2 for “https” URIs with the TLS Application-Layer Protocol Negotiation (ALPN) extension.
  • Calling API Simulator as HTTP and HTTPS proxy and forwarding unmatched HTTP/2 requests over HTTP and HTTPS to the actual HTTP/2 server.
  • Large file or content download with only few MB of memory works with HTTP/2 as it does with HTTP/1.x.
  • HTTP/2 client with support for connecting to a HTTP/2 server using all of the methods: TLS with ALPN extension, prior-knowledge (a.k.a. direct), and upgrade from HTTP/1.1. You would not directly interact with the HTTP/2 client but it is used when forwarding unmatched HTTP/2 requests over HTTP and HTTPS to the actual HTTP/2 server.
  • The same easy DSL (Domain-Specific Language) for modeling simlets.


Known Limitations:

  • The size in the Access Log is always 0 (zero) for HTTP/2 responses.
  • API Recorder only works with HTTP/1.x.

These limitations would not impact your ability to model and run API simulations over the HTTP/2 protocol.


Additional changes and fixes in this release:

  • Added support for case-insensitive URI pattern matching.
  • Fixed a problem with forwarding unmatched HTTP/1.x requests when using TLS/SSL to the actual server.

We keep on innovating and growing API Simulator for you! We’ve got your back when it comes to easy, feature-rich API simulations.


We invite you to learn more about API Simulator, download and install it, and run the examples included in the download. 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!