Admin Tools

#42597 Error 500 when adding AVIF extension in .htaccess Maker

Posted in ‘Admin Tools for Joomla! 4 & 5’

This is a public ticket

Everybody will be able to see its contents. Do not include usernames, passwords or any other sensitive information.

Environment Information

Joomla! version

n/a

PHP version

n/a

Admin Tools version

n/a

Latest post by komir on Saturday, 10 January 2026 02:09 CST

Thursday, 08 January 2026 12:00 CST

komir

Hello,
I am experiencing an issue when trying to enable AVIF support through Admin Tools.

Whenever I add the avif extension to either:

Backend file types allowed in selected directories, or

Frontend file types allowed in selected directories

inside .htaccess Maker, the site immediately throws an Error 500 after saving and rebuilding the .htaccess file.

Removing the AVIF extension restores normal functionality.

Could you please advise what might be causing this issue, and whether Admin Tools requires additional configuration to support the AVIF MIME type?

Thank you in advance.

4M CAD profesionalni CAD alat

Friday, 09 January 2026 01:07 CST

nicholas

You do NOT add MIME types, you add file extensions. You would need to add the item avif without and dots, spaces, or other non-alphanumeric characters.

Beyond that, there's nothing special that would cause this problem. The allowed extensions are simply concatenated in a long string separated by pipes e.g. .7z|.css|.js|.avif. Adding an element there doesn't change anything.

In fact, I did add avif to my dev sites just fine. No problem whatsoever, as expected.

If trying to add AVIF causes an error when you click on Save and Create .htaccess but the avif extension does not appear in the .htaccess, nor do you see the .htaccess last modification time changing, then the problem is 100% outside our software and in your server's configuration. It could be a restriction on the maximum POST size, or a misconfigured security rule which does not like avif, or anything else; ask your host.

Nicholas K. Dionysopoulos

Lead Developer and Director

🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!

Saturday, 10 January 2026 02:09 CST

komir

Thank you for the clarification.

I would like to add one more detail that may help narrow this down.
The issue occurs only when I add avif via Admin Tools → .htaccess Maker. After saving and rebuilding the .htaccess, the site immediately throws an Error 500.

However, if I manually add |avif on the end of line directly to the .htaccess file via cPanel, everything works perfectly and the site loads without any errors.

Best regards