Title: Nik Images Auto Convert
Author: Dmytro Nikolaienko
Published: July 27, 2026
Last modified: July 27, 2026
---
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# Nik Images Auto Convert
By [Dmytro Nikolaienko](https://profiles.wordpress.org/dimon1873/)
[Download](https://downloads.wordpress.org/plugin/nik-images-auto-convert.zip)
* [Details](https://wordpress.org/plugins/nik-images-auto-convert/#description)
* [Reviews](https://wordpress.org/plugins/nik-images-auto-convert/#reviews)
* [Installation](https://wordpress.org/plugins/nik-images-auto-convert/#installation)
* [Development](https://wordpress.org/plugins/nik-images-auto-convert/#developers)
[Support](https://wordpress.org/support/plugin/nik-images-auto-convert/)
## Description
Nik Images Auto Convert does two things.
**New uploads** are converted the moment they arrive, before WordPress generates
the thumbnails, so every registered size is created directly in the new format.
Nothing is converted twice.
**Images already on the site** are converted in bulk. This is the part most plugins
get wrong: renaming `photo.jpg` to `photo.webp` breaks every page that referenced
the old name. This plugin rewrites those references — in post content, custom fields,
widgets, theme options and page builder data — so published pages keep displaying
the same images.
#### What it converts
* JPEG, PNG and GIF, to WebP, AVIF, or the same format (compress only)
* The full size image, every thumbnail size, and the untouched original WordPress
keeps for large uploads
* Animated GIFs are always skipped — converting them would keep only the first
frame
#### How existing content is kept working
* Every URL variant is handled: absolute, protocol relative, root relative, percent
encoded, and the escaped-slash form page builders store in JSON
* Serialized data is unserialized, rewritten and re-serialized so string lengths
stay valid. Values that cannot be rebuilt with certainty are left untouched rather
than risking corruption
* Original files are copied to `wp-content/uploads/nik-iac-originals/`, so any
conversion can be undone
* An optional `.htaccess` rule — written inside the uploads folder, never in the
site root — serves the converted file when something still requests the old URL;
useful for hard coded theme paths, external links and search engine caches
#### Uploading WebP and AVIF files
WordPress permits both formats out of the box, but sites lose them again to security
plugins, host level mime whitelists or themes that overwrite the `upload_mimes`
filter wholesale. The plugin puts them back.
It also rescues uploads that are refused with _“Sorry, this file type is not permitted
for security reasons”_ — which happens when the server’s fileinfo library is too
old to recognise the format and reports it as a plain binary. The extension is never
trusted on its own: such a file is accepted only when its own header proves it really
is WebP or AVIF, so renaming a script to `.webp` still gets it rejected.
#### Safety
* Conversions that would produce a _bigger_ file are skipped and the original is
kept
* EXIF orientation is baked into the pixels, so photos from phones do not end up
sideways
* Colour profiles survive metadata stripping
* Nothing is deleted until the converted file has been written and verified
* A built in test button converts five real images in a temporary folder and reports
the actual saving, changing nothing
#### Requirements
The server needs either the Imagick extension or GD with WebP support. AVIF needs
Imagick built with an AVIF delegate, or PHP 8.1+ for GD. The settings screen tells
you exactly what your server can do.
#### WP-CLI
```
wp nik-images run [--force] [--dry-run] [--limit=]
wp nik-images restore
wp nik-images status
```
#### Privacy
The plugin sends nothing anywhere. All conversion happens on your own server, and
no external service is contacted.
## Installation
1. Upload the plugin to `/wp-content/plugins/nik-images-auto-convert/`, or install
it from **Plugins Add New**.
2. Activate it.
3. Open **Nik Images** in the admin menu, below Settings.
4. Choose a format and quality, then press **Test on 5 images** to see what that quality
actually costs on your own photos.
5. Back up your database, then run the bulk conversion from the **Convert existing
images** tab.
## FAQ
### Will this break my existing pages?
That is precisely what it is built to avoid. Every reference the plugin can reach
is rewritten, originals are kept so the whole thing can be rolled back, and the
optional rewrite rule catches URLs living outside the database. Back up your database
before the first bulk run anyway.
### What quality should I use?
80–85 is visually identical to the original for most photographs. Use the built
in test button: it converts five real images from your library in a temporary folder
and reports the actual saving without changing anything.
### Why did some images stay as JPG or PNG?
Because converting them would have made them bigger. Small flat colour graphics
often compress better as PNG than as WebP, and a photo that was already heavily
compressed can grow when re-encoded. WordPress stores a MIME type per thumbnail
size, so a mixed set works fine.
### Can I undo it?
Yes, as long as “Keep the original files” was enabled. **Nik Images Restore & tools
Restore all originals** puts the files back, restores the attachment records and
rewrites your content back to the original filenames.
### Does deleting the plugin revert my images?
No. Converted images stay converted. Use the restore button first if that is what
you want.
### Does it work with Elementor, ACF or WooCommerce?
Yes. Page builder data stored as JSON, ACF fields stored as serialized meta and
WooCommerce product galleries are all rewritten. Values the plugin cannot rebuild
with absolute certainty are deliberately left alone instead of being corrupted.
### My server has no Imagick. Will it still work?
Yes, if GD has WebP support, which is the case on almost every modern host. The
settings screen shows what is available.
## Reviews
There are no reviews for this plugin.
## Contributors & Developers
“Nik Images Auto Convert” is open source software. The following people have contributed
to this plugin.
Contributors
* [ Dmytro Nikolaienko ](https://profiles.wordpress.org/dimon1873/)
[Translate “Nik Images Auto Convert” into your language.](https://translate.wordpress.org/projects/wp-plugins/nik-images-auto-convert)
### Interested in development?
[Browse the code](https://plugins.trac.wordpress.org/browser/nik-images-auto-convert/),
check out the [SVN repository](https://plugins.svn.wordpress.org/nik-images-auto-convert/),
or subscribe to the [development log](https://plugins.trac.wordpress.org/log/nik-images-auto-convert/)
by [RSS](https://plugins.trac.wordpress.org/log/nik-images-auto-convert/?limit=100&mode=stop_on_copy&format=rss).
## Changelog
#### 1.0.1
* The optional rewrite rules are now written to the uploads folder instead of the
site root, and their path is derived from wp_get_upload_dir() so installs in
a subdirectory work correctly.
* The admin menu item moved below Settings.
#### 1.0.0
* First release.
## Meta
* Version **1.0.1**
* Last updated **19 hours ago**
* Active installations **Fewer than 10**
* WordPress version ** 6.0 or higher **
* Tested up to **7.0.2**
* PHP version ** 7.4 or higher **
* Tags
* [AVIF](https://wordpress.org/plugins/tags/avif/)[compress](https://wordpress.org/plugins/tags/compress/)
[convert](https://wordpress.org/plugins/tags/convert/)[Optimize](https://wordpress.org/plugins/tags/optimize/)
[webp](https://wordpress.org/plugins/tags/webp/)
* [Advanced View](https://wordpress.org/plugins/nik-images-auto-convert/advanced/)
## Ratings
No reviews have been submitted yet.
[Your review](https://wordpress.org/support/plugin/nik-images-auto-convert/reviews/#new-post)
[See all reviews](https://wordpress.org/support/plugin/nik-images-auto-convert/reviews/)
## Contributors
* [ Dmytro Nikolaienko ](https://profiles.wordpress.org/dimon1873/)
## Support
Got something to say? Need help?
[View support forum](https://wordpress.org/support/plugin/nik-images-auto-convert/)