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guideFrequently asked questions

# Why does the editor filter out my content (styles, classes, elements)? Where is config.allowedContent = true?

Unlike CKEditor 4, CKEditor 5 implements a custom data model. This means that every piece of content that is loaded into the editor needs to be converted to that model and then rendered back to the view.

Each kind of content must be handled by some feature. For instance the ckeditor5-basic-styles package handles HTML elements such as <b>, <i>, <u>, etc. along with their representation in the model. The feature defines the two–way conversion between the HTML (view) and the editor model.

If you load some content unknown to any editor feature, it will be dropped. If you want all the HTML5 elements to be supported, you need to write plugins to support them. Once you do that, CKEditor 5 will not filter anything out.

# How to turn the source mode on? How to write a source mode plugin?

Because of the custom data model used in the editor, the source mode makes little sense in CKEditor 5. CKEditor 5 is a content editor, not a page builder and, unless some editor feature (plugin) supports some particular kind of HTML (or any other input format), it will not be accepted as content.

See the relevant issue on GitHub to learn more.

# What happened to the contents.css file? How do I style the content of the editor?

There is no such thing as the contents.css file because in CKEditor 5 features bring their own content styles, which are by default included in the JavaScript build and loaded by the style–loader (they can be extracted, too). It optimizes the size of the builds as the styles of unused features are simply excluded.

Although some styles are provided by the features, it is up to the developers to make sure the content created by CKEditor 5 is properly styled, both in the front–end and in the back–end. To style the content in the editor (back–end), use the .ck-content CSS class:

.ck-content a {
    color: teal;

# The build I downloaded is missing some features. How do I add them?

See the Installing plugins guide to learn how to extend the editor with some additional features.

You can learn which editor features are available in the feature index.

# Where are the editor.insertHtml() and editor.insertText() methods? How to insert some content?

Because CKEditor 5 uses a custom data model, whenever you want to insert anything, you should modify the model first, which is then converted back to the view where the users input their content (called editable). In CKEditor 5, HTML is just one of many possible output formats. You can learn more about the ways of changing the model in the dedicated guide.

To insert a new link at the current position, use the following snippet:

editor.model.change( writer => {
    const insertPosition = editor.model.document.selection.getFirstPosition();
    writer.insertText( 'CKEditor 5 rocks!', { linkHref: '' }, insertPosition );
} );

And to insert some plain text, you can use a slightly shorter one:

editor.model.change( writer => {
    writer.insertText( 'Plain text', editor.model.document.selection.getFirstPosition() );
} );

You may have noticed that a link is represented as a text with an attribute in the editor model. See the API of the model writer to learn about other useful methods that can help you modify the editor model.

To insert some longer HTML code, you can parse it to the model fragment first and then insert it into the editor model:

const content = '<p>A paragraph with <a href="">some link</a>.';
const viewFragment = content );
const modelFragment = viewFragment );

editor.model.insertContent( modelFragment, editor.model.document.selection );

# What happened to the global window.CKEDITOR? How to list all instances of the editor?

By default, CKEditor 5 has no global registry of editor instances. But if necessary, such feature can be easily implemented as explained in the Stack Overflow answer.

# How to enable image drag&drop and upload? Where should I start?

Image features are enabled by default in all editor builds (also the image upload). See the Image and Image upload feature guides to learn more.

# How to use CKEditor 5 with frameworks (Angular, React, etc.)?

There are no ready–to–use framework adapters as of yet. We recognize the popularity of these frameworks and our intention is for the guides and seamless integrations to be developed in the future. Meanwhile, please refer to the GitHub issue for more information.

# How to get a fully–featured editor build (a.k.a. CKEditor 4 “Full Package”)?

We believe each editor build should serve its purpose. Including features that are not used makes little sense because they increase the size of the editor and make the website heavier for no good reason. This is why we do not provide a full editor package similar to what we offer in CKEditor 4.

At the same time, we recommend you to install plugins to enable additional features or even create a custom build to make sure you make the most out of CKEditor 5.

# How to customize the CKEditor 5 icons?

The easiest way is to use webpack’s NormalModuleReplacementPlugin plugin. For example, to replace the bold icon use the following code in your webpack.config.js:

plugins: [
    new webpack.NormalModuleReplacementPlugin(

You can also use the relative path which is resolved relative to the resource that imports bold.svg (the BoldUI class file in this scenario).

Learn more about building CKEditor 5 using webpack.