Sarin is a high-performance HTTP load testing tool built with Go and fasthttp.

Install • Quick Start • Examples • Configuration • Templating

Overview

Sarin is designed for efficient HTTP load testing with minimal resource consumption. It prioritizes simplicity and features like templating add zero overhead when unused.

✅ Supported	❌ Not Supported
High-performance with low memory footprint	Web UI or complex TUI
Dynamic requests via 370+ template functions	Detailed response body analysis
Request scripting with Lua and JavaScript	Distributed load testing
Multiple proxy protocols (HTTP, HTTPS, SOCKS5, SOCKS5H)	HTTP/2, HTTP/3, WebSocket, gRPC
Captcha solving (2Captcha, Anti-Captcha, CapSolver)	Plugins / extensions ecosystem

Installation

Docker

docker run --rm -it aykhans/sarin:latest --version

With a local config file:

docker run --rm -it -v /path/to/config.yaml:/config.yaml aykhans/sarin -f /config.yaml

With a remote config file:

docker run --rm -it aykhans/sarin -f https://example.com/config.yaml

Nix

Run directly without installing (requires flakes enabled):

nix run github:aykhans/sarin/release -- -U http://example.com -r 100 -c 10

Install into your profile:

nix profile add github:aykhans/sarin/release

Or add it to your own flake via the overlay:

{
  inputs.sarin.url = "github:aykhans/sarin/release";

  # In your outputs, apply the overlay to nixpkgs:
  # nixpkgs.overlays = [ inputs.sarin.overlays.default ];
  # then reference pkgs.sarin
}

The release branch tracks the newest stable release cut from main, so nix flake update moves between releases rather than following every commit; pre-releases are excluded. Pin an exact release with github:aykhans/sarin/v1.4.2, or track development with github:aykhans/sarin (the main branch).

Pre-built Binaries

Download the latest binaries from the releases page.

Building from Source

Requires the Go version declared in go.mod.

git clone https://github.com/aykhans/sarin.git && cd sarin

CGO_ENABLED=0 go build \
    -ldflags "-X 'go.aykhans.me/sarin/internal/version.Version=dev' \
    -X 'go.aykhans.me/sarin/internal/version.GitCommit=$(git rev-parse HEAD)' \
    -X 'go.aykhans.me/sarin/internal/version.BuildDate=$(date -u +%Y-%m-%dT%H:%M:%SZ)' \
    -X 'go.aykhans.me/sarin/internal/version.GoVersion=$(go version)' \
    -s -w" \
    -o sarin ./cmd/cli/main.go

Quick Start

Send 10,000 GET requests with 50 concurrent connections and a random User-Agent for each request:

sarin -U http://example.com -r 10_000 -c 50 -H "User-Agent: {{ fakeit_UserAgent }}"

Run a 5-minute duration-based test:

sarin -U http://example.com -d 5m -c 100

Use a YAML config file:

sarin -f config.yaml

For more usage examples, see the Examples Guide.

Configuration

Sarin supports environment variables, CLI flags, and YAML files. When the same option is specified in multiple sources, the following priority order applies:

CLI Flags (Highest) > YAML > Environment Variables (Lowest)

For detailed documentation on all configuration options (URL, method, timeout, concurrency, headers, cookies, proxy, etc.), see the Configuration Guide.

Templating

Sarin supports Go templates in URL paths, methods, bodies, headers, params, cookies, and values. Use the 370+ built-in functions to generate dynamic data for each request.

Example:

sarin -U "http://example.com/users/{{ fakeit_UUID }}" -r 1000 -c 10 \
  -V "REQUEST_ID={{ fakeit_UUID }}" \
  -H "X-Request-ID: {{ .Values.REQUEST_ID }}" \
  -B '{"request_id": "{{ .Values.REQUEST_ID }}"}'

For the complete templating guide and functions reference, see the Templating Guide.

License

This project is licensed under the MIT License. See the LICENSE file for details.