Custom CSS


Custom CSS is a feature for advanced users. There is no official support for customizations, and you perform any customizations at your own risk. In case something goes wrong, you can simply remove the custom.css from the Zettlr data directory to reset the custom CSS again.

It is possible to use custom CSS (Cascading Style Sheets) to modify the complete appearance of the app. You can find the Custom CSS editor in the assets manager.


The examples in this document haven't been updated in some time, so they may not work out of the box.

If you are unfamiliar with CSS, but don't want to simply copy & paste the guides on this page, you may choose to follow a short tutorial on CSS. There are many on the internet, so a quick Google search can also provide you with video tutorials, if you prefer those.

Writing CSS for Zettlr

The styles of Zettlr are divided into both geometry and the actual theme, so you may want to stick with only changing the design of elements without changing any geometry. Playing around with the geometry may be fun, but it may yield completely random behaviour, as some parts of the app depend upon the correct sizes of elements. In case you made a mistake, don't worry: Simply remove the custom.css file from the data directory of Zettlr. You can find the data directory of your own system by looking at the paths provided in the setup guide.

Classes and IDs in Zettlr are always namespaced to the respective components (unless they're global), so to really override a rule you will have to use the complete namespace (you can also use the !important override rule, but this is widely regarded as bad practice).

Everything is always namespaced to the body, which has a class .dark if the app is currently in dark mode. So to make sure a certain rule only applies while the app is in dark mode, make sure to prefix it with body.dark!

Tips for finding selectors

Zettlr's styles are subject to constant changes. While they should remain fairly stable, changes can be introduced in any version, and therefore, instead of providing you with ready-made examples, this page covers how you can find the correct selectors easily.

First of all, make sure to enable the debug mode in the advanced preferences in order to enable the Develop menu. Next, open the developer tools from within this menu and make sure to select the "Elements" tab.

Zettlr with the developer tools open

Then click the arrow in the top-left corner of the developer tools. Now you can click any element in the application to focus it in the developer tools. In the bottom area of the developer tools, you will then see the CSS directives used to style all elements of this particular shape.

The CSS directives in the developer tools

The top rules always override the bottom rules, so what you are interested in is the following directive:

body .cm-quote, body .cm-link, body .cm-strong, body .cm-em {
    color: var(--c-primary);

This is the selector you want to copy over to your custom CSS dialog and style to your liking. As you can see, it gives blockquotes, links, bold and italic text the primary color of the theme.

CSS Code Snippets

Using a Custom Font with Zettlr

In case you do not like the default font delivered with Zettlr, or need to change it, simply paste the following code snippet into the custom CSS editor. Replace your-font-name with the full name of the font you want to use for Zettlr. Please replace placeholder according to the font:

  • In case you want to use a serif font, such as Times New Roman, or Georgia, please use serif
  • In case your font is sans serif, such as Arial or Helvetica, please use sans-serif
  • In case you want to switch to the classic monospace, please use the placeholder monospace

The placeholder will make sure that even if your font cannot be found, an equivalent font will be used. It serves as a fallback. Also, if your font name contains spaces, make sure to surround it with quotation marks, e.g., "Times New Roman".

body .main-editor-wrapper .cm-editor{
    font-family: '<your-font-name here>', <placeholder>;

Custom Background Images

With the following code, you can make your editor have a different background image everytime you start it. The images are taken from, a nice site with free photos. It uses the Source API, which will simply spit out a different image every time the URL is visited. You can test it out by simply visiting the page and refreshing a few times! Please refer to the Unsplash Source API reference for more options (such as using an image of the day).


You can also use a local image as a background image by replacing the corresponding line by background-image: url('file:////absolute/path/to/your/file.jpg');

/* Enter your custom CSS here */

.main-editor-wrapper .cm-editor{
    background-color: transparent;
    background-image: url('');
    background-size: cover;
    background-position: center center;

body .main-editor-wrapper .cm-editor .cm-content{
    background-color: rgba(255, 255, 255, .8);
body .main-editor-wrapper .cm-editor{
    background-color: rgba(255, 255, 255, .8);
body.dark .main-editor-wrapper .cm-editor .cm-content{
    background-color: rgba(0, 0, 0, .8);

Light Mode A preview of a Zettlr installation using above snippet

Dark Mode A preview of a Zettlr installation using above snippet

Visualising Line Endings

In case you want to see where your linefeeds are, you can display the pilcrow symbol (¶) at the end of your lines by using the following Custom CSS:

.cm-line:not(:last-child)::after {
  content: "¶";
  color: #666;

A preview of Zettlr using above snippet

Change the Active Line Styling in Typewriter Mode

You can change the styling of the active line in Typewriter mode. Replace top-border-hex-code, bottom-border-hex-code and background-hex-code in the CSS snippets below with your preferred Hex colour codes, which you can choose from a website such as HTML Color Codes. You may want to have different colour styling for light and dark mode.

Light mode

body .main-editor-wrapper .cm-editor .cm-content .typewriter-active-line {
  border-top: 2px solid <top-border-hex-code>;
  border-bottom: 2px solid <bottom-border-hex-code>;
  background-color: <background-hex-code>;

Dark mode

body.dark .main-editor-wrapper .cm-editor .cm-content .typewriter-active-line {
  border-top: 2px solid <top-border-hex-code>;
  border-bottom: 2px solid <bottom-border-hex-code>;
  background-color: <background-hex-code>;


The example CSS Code Snippets above have been updated and tested with v3.0.1 and so should work with newer versions of Zettlr, but the ones below haven't been updated in some time, and are unlikely to work out of the box.

Set a maximum width for the text

If you have a large screen, you may find that lines of your text are very long. If you wish to have shorter lines in the editor, with margins on both sides, you can use the following CSS snippet:

#editor {
  --side-margin: calc( 50vw - 30em ); 

#editor .CodeMirror {
  margin-left: var(--side-margin);

#editor .CodeMirror-scroll {
  padding-right: var(--side-margin);

A preview of Zettlr using above snippet

For the distraction free mode, the CSS snippet needs to be modified as follows:

#editor.fullscreen {
  --side-margin-fullscreen: calc( 50vw - 30em ); 

#editor.fullscreen .CodeMirror-fullscreen {
  margin-left: var(--side-margin-fullscreen) !important;

#editor.fullscreen .CodeMirror-fullscreen .CodeMirror-scroll { 
  padding-right: var(--side-margin-fullscreen) !important; 

By adjusting the calc functions for the two different modes, the same line width can be achieved with and without the file manager/sidebar.