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—features like templating add zero overhead when unused.

✅ Supported	❌ Not Supported
High-performance with low memory footprint	Detailed response body analysis
Long-running duration/count based tests	Extensive response statistics
Dynamic requests via 320+ template functions	Web UI or complex TUI
Multiple proxy protocols (HTTP, HTTPS, SOCKS5, SOCKS5H)	Scripting or multi-step scenarios
Flexible config (CLI, ENV, YAML)	HTTP/2, HTTP/3, WebSocket, gRPC

Installation

Docker (Recommended)

docker pull aykhans/sarin:latest

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

Pre-built Binaries

Download the latest binaries from the releases page.

Building from Source

Requires Go 1.25+.

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

CGO_ENABLED=0 GOEXPERIMENT=greenteagc 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:

YAML (Highest) > CLI Flags > 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 320+ built-in functions to generate dynamic data for each request.

Example:

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

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.