HTML Mark Tag: Highlighting Text

Aashutosh Dwivedi24 Mar, 2026

In this artcle, we will break down how to use the Mark Tag, how to customise the color, and what to do if you find it is not working in outlook or other email clients.

What is the HTML Mark Tag?

The element is an HTML5 tag designed to represent text that is "marked" or "highlighted" for reference purposes. Imagine searching for a word on a webpage; the browser often uses this tag to show you exactly where that word appears.

Basic Syntax for Mark Tag

To use it, you simply wrap your text within the opening and closing tags. Example: Do not forget to buy milk on your way home. In this instance, the word "milk" will appear with a bright yellow background in almost all modern web browsers. Browser Support and Default Style

The tag works in all major modern browsers and is commonly used to highlight important or relevant text.
It supports global attributes like class, id, title, and style.
It also supports event attributes such as onclick, onmouseover, and other standard HTML events.
By default, most browsers show text with a highlighted background and dark text. This default styling helps marked words or phrases stand out clearly within a sentence or paragraph.

Use Of HTML Mark Tag

Standard formatting like (bold) or (italics) changes the visual weight of the text. But the Mark Tag is semantic. This snippet lets the browser and assistive technologies (like screen readers) know that it is important in this situation.

Search Results: Showing the word that the user looked for.
Study Guides: Highlighting important definitions in a course.
Quotations: Drawing attention to a certain element of a long quote without modifying how the original author emphasised it.

HTML Mark Tag Change color

The default yellow is standard, although it might not always look good with your website's style. CSS (Cascading Style Sheets) makes it easy to adjust the colour. Developers frequently call this the process of changing the colour of the mark tag.

Using Inline CSS

If you want to change a single instance, you can use the style attribute: Highlighted in Cyan

Using Internal/External CSS

For a cleaner approach, define it in your stylesheet: mark { background-color: lightgreen; color: black; }

HTML Mark Tag with Different Color

You can create multiple classes if you want to use the different color options across your site. For example:

.important { background-color: red; color: white; }
.note { background-color: orange; }

Mark vs. Other Formatting Tags

It is easy to get confused between various text-formatting tags. Here is a simple breakdown to help you choose the right tool for your project.

Tag	Purpose	Visual Effect
<mark>	Highlighted for relevance	Yellow background (default)
<strong>	Strong importance/urgency	Bold text
<em>	Stress emphasis	Italic text
<u>	Unarticulated non-textual	Underlined text

Technical Issues in HTML Mark Tag

A common frustration for developers is HTML Mark Tag not working in outlook.

Why does it fail in Outlook?

Microsoft Outlook uses a rendering engine that is often based on Word, which does not fully support all HTML5 tags. If you are designing an HTML email and notice the highlight isn't showing up, the tag is likely being ignored.

The Solution

To fix this, avoid the tag entirely for emails. Instead, use a tag with inline styles: Your text here This method is much more "bulletproof" and ensures that your highlight appears across different email apps like Gmail, Outlook, and Apple Mail. Also read :

Implementing Mark Tag in HTML

If you are practicing your skills, try building a simple "Search Result" simulation.

Open your text editor (like Notepad or VS Code).
Create a basic HTML structure.
Inside the body, write a paragraph.
Apply the Mark Tag to the keywords.
Save as index.html and open it in Chrome or Firefox.

Advanced Customisation and Browser Behavior with HTML Mark Tag

Tthere are more advanced ways to style it that may make a website look new and elegant.

Beyond Solid Colours: Using Gradients

Instead of a flat, solid yellow, many modern websites use linear gradients to create a "partial highlight" effect. This makes it look like a real highlighter pen was used across the bottom half of the text. You can achieve this by using the background property instead of just background-color. Example CSS: mark { background: linear-gradient(180deg, rgba(255,255,255,0) 50%, #ffeb3b 50%); } This creates a stylish, half-filled highlight that is very popular in contemporary web design. It keeps the text legible while adding a touch of personality to the Mark Tag in HTML.

Accessibility and Contrast

When you decide to implement a different color, you must consider accessibility. If you choose a dark background color, like navy blue, for your highlight, the default black text will become impossible to read. Always pair a dark background with a light text color: mark.dark-mode { background-color: #000080; color: #ffffff; }

Browser Support and Fallbacks

The good news is that the Mark Tag in HTML is supported by all modern browsers (Chrome, Firefox, Safari, Edge). However, for extremely old browsers or specific environments where the Mark tag is not working in outlook is an issue, providing a fallback style is a sign of a professional developer. By using the span tag workaround mentioned earlier, you ensure that your "marked" text remains highlighted even in the most restrictive viewing environments. By paying attention to these small technical details, you ensure that your use of the Mark tag is not just functional, but also beautiful and inclusive for all users.

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FAQs

Is it possible to use Mark Tag with different color options on the same page?

Yes, with the help of CSS classes, you can define multiple styles for different color backgrounds like pink, blue, or green to categorise information.

Why is the Mark Tag in HTML not working in outlook emails?

Outlook has limited support for HTML5. To ensure highlighting works in emails, use a tag with an inline background-color style instead of the tag.

How do I perform a Mark Tag in HTML change color via CSS?

You can change the color by targeting the mark selector in your CSS and setting the background-color property to your preferred hex code or color name.