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curl-loader is an open-source software performance testing tool written in the C programming language.

curl-loader is capable of simulating application behavior of hundreds of thousands of HTTP/HTTPS and FTP/FTPS clients, each with its own source IP-address. Unlike other tools, curl-loader is using real C-written client protocol stacks, namely, HTTP and FTP stacks of libcurl and TLS/SSL of openssl, and simulates user behavior with support for login and authentication flavors.

The goal of the project is to deliver a powerful and flexible open-source testing solution as a real alternative to Spirent Avalanche and IXIA IxLoad.

The tool is useful for performance loading of various application services, for testing web and ftp servers and traffic generation. Activities of each virtual client are logged and collected statistics includes information about resolving, connection establishment, sending of requests, receiving responses, headers and data received/sent, errors from network, TLS/SSL and application (HTTP, FTP) level events and errors.

The tool can be easily extended to generate sftp, telnet, tftp, ldap, ssh, scp etc other application protocols, supported by the libcurl library.

 curl-loader 0.56

Free to download



Robert Iakobashvili, Michael Moser


System Requirements

Support Sites:
FAQ, SourceForge Project Page, Mailing List

Selected Reviews:

Features include:

  • Virtual clients number. The tools runs depending on your hardware and scenario 5,000-25,000 and more simultaneously loading clients, all from a single curl-loader process. Actual number of clients may be several times higher, and is limited mainly by the system memory. Each client performs loading from its own source IP-address or, as an option, all clients share the same IP-address
  • Rampup of the virtual clients number at loading start in either automatic or manual mode
  • IPv4 and IPv6 addresses and URIs
  • HTTP 1.1. GET, POST, PUT, DELETE, HEAD including file upload operations
  • HTTP user authentication login with POST or GET+POST methods. Unique configurable username and password for each virtual client as well as configurable posted string (post-forms) are the options. Another option is loading of users with credentials from a tokens text file
  • HTTP POST/GET forms with up to 16 tokens filled from a tokens text file
  • HTTP user logoff with POST, GET+POST, or GET (cookies)
  • POST logoff with configurable posted string (post-forms)
  • HTTP multipart form data POST-ing as in RFC1867
  • HTTP Web and Proxy Authentication (HTTP 401 and 407 responses) with Basic, Digest (RFC2617) and NTLM
  • HTTP 3xx redirections with unlimited number of redirections
  • HTTP cookies and DNS caches
  • FTP passive and active, FTP upload
  • Full customization of client request HTTP/FTP headers
  • Transfer limit rate for each client download or upload operation on a per url bases
  • URL fetching probability
  • TCP connections reuse or re-establishment on a per URL bases
  • Unlimited configurable number of URLs. Mixing of HTTP, HTTPS, FTP and FTPS urls in a single batch (test plan) configuration
  • Connection establishment timers for each URL
  • URL completion timers monitoring and enforcement for each client
  • Inter/after URL "sleeping" timers, including random timers taken from a configurable interval
  • Logfile with tracing activities for each virtual client
  • Logging of responses (headers and bodies) to files
  • Pre-cooked batch configuration (test plan) examples
  • Load Status at console and with output to file
  • Status and statistics for each virtual client which are logged to file;

curl-loader in action

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Last Updated Friday, July 03 2015 @ 08:11 AM EDT

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