For this to work, the HTML file and the CSS file must be stored in a a folder that is fully accessible by Textastic: so the two files must both be stored in the same folder in either "Local Files", "iCloud" or in an external folder.

It seems like you opened the files as individual external files (e.g. using the "Open…" command). In this case, Textastic only gets access to the single file, not to the containing folder. If a file opened in such a way references another file, the app cannot access it.

This is mentioned in the manual at: https://www.textasticapp.com/v10/manual/integration_other_apps/external_files_folders.html

If you plan to use the built-in web preview to preview a HTML file with external JavaScript, CSS, or image files, it is recommended to use one of the built-in clients for (S)FTP, WebDAV, Dropbox, or Google Drive to download your website files first and edit and preview them locally. If you open a single file with the document picker, linked files cannot be accessed by the web preview due to the iOS security sandbox that limits an app’s access to files in other apps.

I had not, but I just opened it right now. 

Is there a problem with it? It does not hang for me anymore with the latest beta.

Thanks a lot for sending me your syntax definition. 

I could reproduce and fix the problem. It was an issue with "embed" operations.

This should be fixed in the new beta I just released.

Can you please send me your custom HTML syntax highlighting as a .zip file so I can try to reproduce the issue?

So, is this a new bug or did this happen before the latest beta, too?

I can see your crash in App Store Connect / TestFlight. In fact, I see several from you also from past TestFlight versions. Unfortunately, there seems to be no crash details attached.

Do you have any customizations in the "Local Files/#Textastic" folder?

Can you send me a screen recording of the hang and crash? Maybe it helps me reproduce the issue.

Hello,

it works fine on my devices, so can you please answer some questions?

• How exactly are you opening the HTML file? Where is the file stored? 
• Which theme are you using?
• Can you send me the file that causes the crash? 

Thanks!

I've been bitten by this behaviour myself. I think I'll change it so that auto indentation is not applied to the last line when pasting multiple lines of code.