FileZilla - FileZilla is an FTP, or file transfer protocol, client. It lets individuals transfer single files or batches to a web server. For many years, FTP was the standard for website design. Read more about FileZilla.
Beeceptor - Unblock yourself from API dependencies, and build & integrate with APIs fast. Beeceptor helps you build a mock Rest API in a few seconds.
HTTPie - CLI HTTP that will make you smile. JSON support, syntax highlighting, wget-like downloads, extensions, and more.
Webhook.site - Instantly generate a free, unique URL and email address to test, inspect, and automate (with a visual workflow editor and scripts) incoming HTTP requests and emails.
Yummy FTP Pro - Pro-level, fast, reliable FTP/S + SFTP + WebDAV/S client.
MockServer - Easy mocking of any system you integrate with via HTTP or HTTPS.