siege

Test a URL with default settings (15 concurrent users)

$ siege [https://example.com/]

$ siege -c [50] -t [1M] [https://example.com/]

$ siege -b -c [100] -t [30S] [https://example.com/]

$ siege -f [urls.txt]

$ siege -i -f [urls.txt] -c [25] -t [5M]

$ siege -d [2] -c [10] [https://example.com/]

$ siege -g [https://example.com/]

$ siege -C

siege [options] [URL]

siege is a multi-threaded HTTP/HTTPS load testing and benchmarking utility. It simulates multiple concurrent users accessing a web server to measure performance under stress. Metrics reported include response time, transaction rate, throughput, concurrency, and availability.
The tool operates in three modes: regression (sequential URL testing), internet simulation (randomized access patterns with -i), and brute force benchmarking (maximum throughput with -b).
By default, each simulated user pauses randomly between requests to simulate realistic traffic. The -d option controls this delay range, while -b eliminates it entirely for pure throughput testing.
Configuration is stored in ~/.siege/siege.conf. URLs can be specified on the command line or in a file with -f, supporting POST data and custom headers.

-c, --concurrent num

Number of concurrent simulated users (default: 15)

Number of repetitions per user; "once" runs each URL once

Run duration with modifier: S (seconds), M (minutes), H (hours)

Random delay (0 to num seconds) between requests per user

Benchmark mode; removes delays for maximum throughput

Read URLs from a text file

Simulate internet traffic by randomizing URL order

Display HTTP headers for a single request

Display headers and response body

Override the User-Agent header

Add custom request header

Override Content-Type header

Show detailed output with color-coded responses

Suppress output; useful for scripts

Write results to specified log file

Display current configuration settings

~/.siege/siege.conf

User configuration file for default concurrency, delay, logging, protocol version, and other settings. Generated with siege.config.

Default URL file used when no -f option or URL argument is provided.

High concurrency levels can overwhelm target servers and may constitute a denial-of-service attack. Always obtain permission before load testing servers you do not own. Some hosting providers prohibit load testing in their terms of service.

siege was created by Jeffrey Fulmer (JoeDog) and first released around 2000. It was designed to help web developers measure their code's performance under load. The tool has been actively maintained and updated to support modern HTTP features including HTTPS and HTTP/1.1.

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