PostmanCanary 9.12 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. We recommend checking the downloaded files with any free antivirus. The application lies within Developer Tools, more precisely Webmaster Tools. The most recent installation package that can be downloaded is 124.3 MB in size. The actual developer of this free Mac application is Postman, Inc.
From the developer:
Postman Canary executes requests, scripts and tests on Postman’s native apps. Postman Canary can be downloaded and run separately from the main Postman app. Of course, if you have a Postman account, you can sync seamlessly between the production and the Canary apps to get a test of the new features without disturbing your workflow.
You may want to check out more software for Mac, such as ModelBaker, iGooMap or PageRank Viewer, which might be similar to PostmanCanary.