Cetus Image Converter & AI Alt Text

Next-Gen WebP & AVIF Conversion with AI-Powered Alt Text

Automated image optimization and smart SEO accessibility for WordPress. Convert your entire media library to AVIF or WebP, auto-generate Alt Text via Google Gemini or OpenAI, detect orphan files, and track savings: all from a single native admin panel.

Features

• AVIF / WebP conversion: Creates optimized copies alongside originals (JPG/PNG/GIF are never deleted). Uses Imagick when available, falls back to GD.
• Smart format selection: Automatic mode picks AVIF when the server supports it, WebP otherwise. Force a specific format if needed.
• WebP → AVIF re-conversion: Already have WebP images? Convert them to AVIF without re-uploading.
• Auto-convert on upload: Optionally convert every new image the moment it lands in the library.
• AI-powered Alt Text: Send images to Google Gemini or OpenAI (BYOK) and save descriptions natively as _wp_attachment_image_alt. Automatic fallback between providers on quota errors.
• Bulk processor: Asynchronous AJAX batches with real-time progress bar, speed (img/s), ETA, Pause and Stop controls. Safe for shared hosting.
• WP-Cron background processing: Process the library unattended without keeping the browser open.
• Orphan file scanner: Finds images on disk not registered in the WordPress database.
• Conversion log: Scrollable table of the last conversions with format, space saved and status.
• Per-image exclusion: Skip individual images from both auto-convert and bulk batch via the attachment edit screen.
• Library statistics: Total images, unconverted count, disk usage by format, cumulative savings.

Requirements

Feature	Requirement
WebP output	Imagick with WebP or GD with WebP
AVIF output	Imagick with libavif / libheif
AI Alt Text	Google Gemini or OpenAI API key (BYOK)
WordPress	6.2 or later
PHP	8.0 or later

The built-in Step 1, Server Diagnosis panel shows green/red indicators for every capability on your specific server.

Installation

1. Upload the cetus-media-optimizer folder to /wp-content/plugins/.
2. Activate through Plugins in the WordPress admin.
3. Go to Cetus Media in the admin menu.
4. Follow the three-step panel:
   • Step 1: Review server diagnostics.
   • Step 2: Choose output format and optionally add AI API keys.
   • Step 3: Click Start Optimisation to process the library.

Privacy & Security

• All AJAX handlers require a valid WordPress nonce and current_user_can('manage_options').
• Original images are never deleted: conversion only adds companion files.
• API keys are stored in the WordPress options table and are never exposed in front-end HTML or JavaScript.
• AI requests go directly from your WordPress installation to Google or OpenAI: no data passes through a server of ours.

The three services this plugin can talk to

Nothing here happens unless you turn it on. The full disclosure, in the form WordPress.org requires, is under External Services in readme.txt.

Google Gemini and OpenAI, for alt text. Called only when you have entered an API key and started a conversion. The image goes as a Base64 payload directly from your site to the provider you chose.

Sentry, for crash reports. This one is worth reading carefully, because it is the only feature that sends anything without you starting it:

• It is off by default and needs an explicit opt-in under Cetus Media → Preferences → Telemetry.
• With it on, a PHP error inside the plugin is reported. before_send drops any event whose stack trace does not pass through this plugin's own files, so a fault in your theme or in another plugin is discarded rather than sent.
• What leaves the site: error type, the stack trace, WordPress version, PHP version, plugin version. The user object is emptied, send_default_pii is off, and the Cookie, Authorization, X-Forwarded-For, X-Real-IP and HTTP_CLIENT_IP headers, the cookies, the environment and the URL are all stripped before the event is transmitted. Tracing and profiling are at 0.
• The plugin registers its own section in Tools → Privacy, so what it does is stated where WordPress expects your visitors to be told about it.
• The DSN is not in this repository. %%SENTRY_DSN%% is a placeholder that the release workflow substitutes; without it, init() returns before Sentry is ever started. Building this repository yourself therefore produces a plugin with no telemetry at all, even if the switch is on.

The implementation is in includes/class-cetus-telemetry.php, and it is short enough to read in full before deciding whether you believe it.

Development

# Install dev dependencies
composer install

# Run PHP_CodeSniffer
composer phpcs

# Fix what it can fix automatically
composer phpcbf

CI runs PHPCS against the WordPress Coding Standards and a syntax check on PHP 8.0 through 8.3, on every push. See .github/workflows/.

How to report, propose and build is in CONTRIBUTING.md.

Reporting a security problem

Not in a public issue: use the Security tab, then Report a vulnerability. This plugin holds API keys and writes into the media library of somebody else's site, so a report stays private until there is a fix. What counts as one here, and what does not, is in SECURITY.md.

Changelog

See CHANGELOG.md for the full history.

Support

• WordPress.org forum: https://wordpress.org/support/plugin/cetus-media-optimizer/
• GitHub Issues: https://github.com/skapacraft/cetus-media-optimizer/issues
• Email: support@skapacraft.com

Author

Developed and maintained by SkapaCraft (skapacraft.com).

Trademarks

Not affiliated with, endorsed by or sponsored by Google LLC, OpenAI or Functional Software, Inc. Google, Gemini, OpenAI and Sentry are trademarks of their respective owners, named here only to identify the services this plugin can be configured to call.

Licence

Copyright (C) 2026 SkapaCraft. GPL-2.0-or-later, see LICENSE.

WordPress requires the GPL, and it suits a plugin that can be configured to send crash reports off the site: whatever it does with that data, you can read the code that does it and change it.

Naming

Three names refer to the same thing, and all three are correct in their own place. Cetus Image Converter & AI Alt Text is the published product name, on WordPress.org and in the admin. cetus-media-optimizer is the WordPress.org slug, which is fixed once a plugin is published, and therefore also the name of this repository and of the plugin directory.