Testing Dark Reader Chrome extension's addition of darkreader CSS styles to HTML of blog post edited in Compose mode

Last updated on 28 Apr 2026

Late April 2026 Update

Subsequent tests and analysis conducted in late April 2026 (detailed in In Dark Reader extension On state, sometimes Blogger Edit Post HTML temporarily shows Dark Reader attributes and styles) have shown that certain conclusions in this post are no longer reliable. 

Specifically, the finding that typing directly in Compose mode while the Dark Reader extension is "On", does not inject CSS bloat is unreliable. As we do not have access to Blogger Edit Post source code, it is still not clear to me exactly when and how Blogger introduces the darkreader attributes and styles, when Dark Reader is On. But some tests confirm that Blogger does inject it at times. Therefore it is not reliable or safe to make presumptions about Blogger not introducing Dark Reader attributes and styles in some use cases, when Dark Reader is On. The safe approach to prevent darkreader attributes and styles getting injected into blog post content is to ensure that Dark Reader extension is Off whenever editing a Blogger blog post.

However, the tests mentioned or referred to in this post, showing that editing is safe when the extension is toggled "Off" in its UI—even while remaining enabled in the browser—remain valid. It is not necessary to completely uninstall or disable the extension in the browser settings; simply toggling it off for Blogger ensures clean HTML generation.

Note that when Dark Reader extension is Off, you can use Windows High Contrast (keyboard shortcut: Left Shift + Left Alt + PRINT SCREEN), to see Blogger post content in gray. But in Blogger Post Edit HTML view, text selection or even find highlight is not visible, at least with my Windows 11 settings. 

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Test to see if Compose adds darkreader CSS styles (e.g. --darkreader-inline-color) even when Dark Reader extension is enabled but is switched 'Off' temporarily in its UI.

Identifying Blogger blog posts with size bloat

This test confirms that adding text and a link in Compose when Dark Reader extn. is enabled but switched 'Off' does NOT add darkreader CSS styles to Blogger post. I used HTML view to check the generated HTML.

Now I will switch 'On' Dark Reader extn. and repeat the same addition of text and a link in Compose mode.

Test to see if Compose mode adds darkreader CSS styles when Dark Reader extension is enabled and is switched 'On'.

Identifying Blogger blog posts with size bloat

This test confirms that adding text and a link in Compose when Dark Reader extn. is enabled and switched 'On' does NOT add darkreader CSS styles to Blogger post. I used HTML view to check the generated HTML.

Now I will copy-paste text from a blog post to this Compose window. Dark Reader extension is enabled and is switched 'On'.

Quick Info

Details

This post follows up my previous post: Fixing Gemini chat to Blogger Compose post copy-paste causing 1.5 MB post size bloat due to unnecessary CSS.


Gemini chat: Blogger Feed Request Issue

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This operation brought it lot of darkreader CSS styles into the blog post.
Further even these lines that I am typing in Compose mode which are part of the div holding the above copy-paste content, have darkreader CSS styles applied to them.


New div created in HTML view

Now I am typing in Compose view but that is going either inside a fresh div I created in HTML view or just after it. This text does not have darkreader CSS styles applied to it.


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