Securimage — Free PHP CAPTCHA Script

Quick Start

Download Securimage

composer require dapphp/securimage
# or download from https://github.com/dapphp/securimage

Show the CAPTCHA image

<?php
require 'securimage/securimage.php';
$img = new Securimage();
$img->show(); // outputs CAPTCHA image and stores code in session

Validate on form submit

<?php
require 'securimage/securimage.php';
$img = new Securimage();
if ($img->check($_POST['captcha_code']) === false) {
    die('Incorrect CAPTCHA. Please try again.');
}
// CAPTCHA passed — process the form

What is Securimage?

Securimage is an open-source, free PHP CAPTCHA script for generating complex images and CAPTCHA codes to protect forms from spam and abuse. It can be added to any existing PHP form in minutes — no API keys, no external services, no data sent to third parties. As long as your server has PHP and the GD extension, Securimage works.

The library has been used by PHP developers worldwide since 2008 and is actively maintained on GitHub under the GPL license.

Features

Display a CAPTCHA image in 3 lines of code
Validate submitted codes in under 6 lines
Fully self-hosted — no external API calls or third-party data collection
Customisable code length, character set, and image size
TTF font support for unique, hard-to-solve images
Random background images for added bot resistance
Adjustable distortion (perturbation) and line overlay
Audible CAPTCHA support (WAV audio files) for accessibility
Word-list mode for real-word CAPTCHA codes
WordPress plugin available (Securimage-WP)
PHP 8 compatible
GPL-licensed — free for any use

Evaluating Your Options in 2026?

Securimage remains an excellent choice when you need a self-hosted, zero-dependency CAPTCHA with no external data collection. But the CAPTCHA landscape has changed significantly since 2008. Cloudflare Turnstile, hCaptcha, and reCAPTCHA v3 offer invisible or near-invisible bot detection that many users prefer.

We cover the full landscape in our CAPTCHA alternatives guide — an honest comparison of every major option in 2026, including when Securimage is still the right choice.

Download & Source Code

Securimage is available on GitHub. The latest release supports PHP 7.2+ through PHP 8.x.

View on GitHub → Quickstart Guide →

Securimage: Free Open-Source PHP CAPTCHA

Free & Open Source

PHP 8 Compatible

CAPTCHA Alternatives