Description

Sasim WebP Auto Converter creates WebP copies of your JPEG and PNG uploads and automatically outputs them on the front end — no theme code required.

Plug & play (enabled by default)

Featured images (the_post_thumbnail)
wp_get_attachment_image() output
Images in post content, text widgets, and block widgets
Responsive <picture> with WebP <source> when sibling files exist

Disable under Settings WebP Converter if your theme uses custom image helpers.

Conversion

Configurable WebP quality (0–100)
Batch tool for existing media library images
Prefers WebP URLs in srcset when a sibling .webp file exists
Removes WebP siblings when the attachment is deleted
Uses Imagick when available, falls back to GD

Requirements

PHP 7.4+
GD with WebP support (imagewebp) or Imagick with WebP support

Privacy

This plugin processes images only on your server. It does not collect, store, or transmit personal data to external services. Batch conversion runs via authenticated admin AJAX only.

External services

This plugin does not connect to third-party services. Image conversion uses your server’s GD or Imagick extension only.

Screenshots

Settings page with status strip, quality slider, and batch conversion

Automatic WebP generation on upload — Settings page with status strip, quality slider, and batch conversion

Installation

From WordPress.org (after approval)

Go to Plugins Add New.
Search for Sasim WebP Auto Converter.
Click Install Now, then Activate.

Manual upload

Upload the sasim-webp-auto-converter folder to /wp-content/plugins/.
Activate the plugin through the Plugins menu in WordPress.
Open Settings WebP Converter to adjust quality or batch-convert existing images.

Front-end WebP output works automatically when plug & play is enabled (default).

FAQ

Does this delete my original JPEG or PNG files?: No. The plugin creates additional .webp files alongside the originals. With plug & play enabled, browsers that support WebP receive <picture> markup automatically.
Do I need to edit my theme?: No. Plug & play is on by default. Disable it in settings if your theme already outputs custom <picture> elements and you want to avoid double processing.
Will every visitor receive WebP images?: With plug & play enabled, the plugin outputs <picture> with a WebP <source> when sibling files exist. Browsers that support WebP load the smaller format; others fall back to JPEG/PNG via the <img> tag.
What quality should I use?: 80–85 is a good starting point for photographs. Lower values reduce file size but may reduce visual quality. Re-run batch conversion after changing quality to regenerate existing WebP files.
Does it work on existing uploads?: Yes. Use Generate WebP on the settings page to process the media library in batches.
Does the plugin send data to external servers?: No. All conversion happens locally using PHP GD or Imagick. The batch tool uses WordPress AJAX in the admin only.
What happens on uninstall?: Plugin options are removed. Generated .webp files remain on disk so your site keeps working; delete them manually if you no longer need them.
Does it work with page builders and CDNs?: Plug & play enhances standard WordPress image output. Page builders that bypass core APIs may need theme helpers (see plugin documentation). CDNs that serve your uploads directory will serve .webp siblings when URLs point to them.
Can I use this with other image optimization plugins?: Avoid running multiple plugins that both convert uploads to WebP or rewrite the same image markup. Test on staging first.
Which image formats are supported?: JPEG and PNG uploads are converted. SVG and GIF are not converted. WebP output requires server support (GD imagewebp or Imagick).
Multisite?: Each site has its own settings and media library. Network-activate if you want the plugin available on all subsites.

Reviews

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Contributors & Developers

“Sasim WebP Auto Converter” is open source software. The following people have contributed to this plugin.

Evgenii Sasim

Translate “Sasim WebP Auto Converter” into your language.

Interested in development?

Browse the code, check out the SVN repository, or subscribe to the development log by RSS.

Changelog

1.4.1

WordPress.org directory slug sasim-webp-auto-converter (display name: Sasim WebP Auto Converter)
Prefixed functions, options, AJAX actions, and admin script handles (saswac_*)
Redesigned settings page: status strip, postbox sections, batch progress bar
Quality slider with synced number input
For developers section with theme helpers documentation link
Batch AJAX progress fields: total, processed, converted_batch
Tested up to WordPress 7.1

1.3.0

Plug & play mode: auto-enhance featured images, attachment images, and content (on by default)
Settings toggle to disable front-end auto output
Developer filters: saswac_auto_output_enabled, saswac_should_auto_output, saswac_default_sizes_attr

1.2.1

WordPress-native helpers without ACF: featured image, post meta, options, wp_attachment_image drop-in

1.2.0

Theme helper functions for responsive <picture> WebP output (saswac_*)
Optional the_content filter (disabled by default)
Documentation: docs/theme-helpers.md

1.1.0

WordPress.org release pack: readme, uninstall cleanup, i18n text domain
Batch regeneration for existing media library images
Imagick support with GD fallback
WebP cleanup on attachment delete

1.0.0

Initial release: upload conversion, srcset WebP preference, settings page

Description

Plug & play (enabled by default)

Conversion

Requirements

Privacy

External services

Screenshots

Installation

From WordPress.org (after approval)

Manual upload

FAQ

Does this delete my original JPEG or PNG files?

Do I need to edit my theme?

Will every visitor receive WebP images?

What quality should I use?

Does it work on existing uploads?

Does the plugin send data to external servers?

What happens on uninstall?

Does it work with page builders and CDNs?

Can I use this with other image optimization plugins?

Which image formats are supported?

Multisite?