httpmon

What httpmon is

httpmon is a free terminal-based HTTP and HTTPS debugging proxy for Linux and macOS. It intercepts requests and responses so users can inspect and modify traffic as it happens; methods and status codes are color-coded. For HTTPS inspection, httpmon generates CA certificates automatically, then presents decrypted headers, bodies, and timing in plain text. It can also decode gRPC, gRPC-Web, and Protobuf bodies into readable JSON, including wire-format fields when .proto files are unavailable.

Vim-style navigation and filters for host, path, method, or status code help users move through captured traffic. Request tools include inspecting headers and bodies, composing or repeating requests, copying them as cURL, and comparing requests side by side. JavaScript hooks can modify requests and responses, while throttling presets and local-file serving provide additional traffic controls. Captured flows can be exported as HAR. An MCP server can expose traffic to LLM agents through the Model Context Protocol. The FAQ says it can run over SSH, in Docker containers, and in CI wherever a terminal is available; it starts in milliseconds and uses about 20 MB of RAM. The Free plan is MIT-licensed, requires no account, and has no paid tiers.

Who it suits

httpmon suits developers who want to inspect or alter HTTP and HTTPS traffic from a terminal on macOS or Linux. Its protocol decoding, traffic replay, filtering, and CI, Docker, or SSH availability may also suit teams debugging services in those environments.

Limits

The Free plan is MIT-licensed and has no paid tiers or account requirement. The FAQ identifies macOS and Linux as supported platforms; HTTPS inspection displays decrypted headers, bodies, and timing in plain text.

Getting started

1. Open the httpmon website.
2. Use the terminal-based tool on macOS or Linux.
3. Run it over SSH, in a Docker container, or in CI if useful for your environment.
4. Use its traffic filters and request tools to inspect captured traffic.

Verdict

Choose httpmon if you need a free terminal proxy for inspecting and changing HTTP or HTTPS traffic on macOS or Linux. Its plain-text display of decrypted HTTPS traffic is an important consideration when handling sensitive requests and responses.