HTML Guide
The width and height attributes on <img> elements expect a digit to specify the dimension in pixels. It should not contain units, letters or percent signs.
You can achieve this using CSS instead, for example:
<!-- Invalid syntax, the height attribute expects only digits -->
<img src="photo.jpg" alt="cat" height="auto" />
<!-- Valid syntax using CSS -->
<img src="photo.jpg" alt="cat" style="height: auto" />Learn more:
Related W3C validator issues
The height attribute on the <video> element must be a non-negative integer representing the height in CSS pixels. The value “auto” is not a valid value for this attribute. To resolve the issue, set the height attribute to a specific numeric value or adjust the height using CSS instead.
Example with a numeric height value:
<video width="640" height="360" controls>
<source src="movie.mp4" type="video/mp4">
Your browser does not support the video tag.
</video>Alternatively, control the height using CSS:
<video width="640" controls style="height: auto;">
<source src="movie.mp4" type="video/mp4">
Your browser does not support the video tag.
</video>In the CSS approach, “auto” can be used, but it should not be part of the HTML attributes.
The width attribute on the img element must be a positive integer representing the number of pixels.
The HTML img element’s width and height attributes are expected to specify image dimensions in pixels. According to the HTML Living Standard, these attributes accept only non-negative integers. These integers define the rendered dimension of the image, overriding the actual image size based on its native resolution. The value “auto” is not a valid integer, which leads to the validation error you’ve encountered.
Here is a correct usage example of the img element:
<!DOCTYPE html>
<html lang="en">
<head>
<title>Valid Image Width</title>
</head>
<body>
<img src="example.jpg" alt="Example image" width="200" height="100">
</body>
</html>In the example above, the width is set to 200, and the height is set to 100. Both values are non-negative integers representing pixel dimensions. If you intend to maintain the image’s aspect ratio while adjusting another dimension, you can omit one of the attributes, and modern browsers will automatically adjust the aspect ratio based on the given dimension.
The error message is indicating that the width attribute of the <video> element has an invalid value. According to the HTML specification, the width attribute expects a non-negative integer value, representing the pixel width of the video.
The value "auto" is not valid for the width attribute. Instead, specify a full number that indicates the pixel width of the video. If you want the video to be responsive without specifying a fixed width, you can use CSS to achieve that.
Here are two ways to resolve this:
-
Specify a valid pixel value for width:
<video width="640" height="360" controls> <source src="video.mp4" type="video/mp4"> Your browser does not support the video tag. </video> -
Use CSS for a responsive video player:
Instead of using the width attribute, use CSS to set the width of the video element. This allows the video to adjust its size according to the container or viewport.
<style> .responsive-video { width: 100%; height: auto; } </style> <video class="responsive-video" controls> <source src="video.mp4" type="video/mp4"> Your browser does not support the video tag. </video>
In the second example, the video will scale based on its containing element, maintaining its aspect ratio due to the height: auto; CSS rule. This approach offers more flexibility for responsive design.
The attributes width and height of <iframe> elements expect a non-negative integer, so an empty string is not allowed. Either define the correct dimension, or remove this attribute.
The attributes width and height of <img> elements expect a non-negative integer, so an empty string is not allowed. Either define the correct dimension, or remove this attribute.
The attributes width and height on an iframe expect a valid positive integer without any decimals.
Here’s an example of incorrect code where decimals are being used for dimension attributes:
<iframe src="example.html" height="602.88" width="800.2"></iframe>Corrected code without decimals:
<iframe src="example.html" height="603" width="800"></iframe>In the corrected code, the width and height values has been changed to a whole number, which conforms to the standard integer value expected by the W3C validator.
The attributes width and height on an iframe expect a valid positive integer without any decimals.
Here’s an example of incorrect code where decimals are being used for dimension attributes:
<img src="photo.jpg" alt="Dog" height="602.88" width="800.2">Corrected code without decimals:
<img src="photo.jpg" alt="Dog" height="603" width="800">In the corrected code, the width and height values has been changed to a whole number, which conforms to the standard integer value expected by the W3C validator.
The width and height attributes on <img> and <iframe> elements expect a digit to indicate the number of pixels. Ensure that this attribute contains only digits.
For example:
<!-- This is invalid because width is not a digit -->
<img width="225px" height="100px" alt="cat" src="cat.jpg" />
<!-- This is valid -->
<img width="225" height="100" alt="cat" src="cat.jpg" />The <table> element does not accept a height attribute. Use CSS instead.
The W3C HTML Validator issue you encountered indicates that the value of the height attribute for an <img> element is set to “100%”, which is not allowed in HTML. The height attribute must be a specific digit that represents the height in pixels (e.g., “150”), rather than a percentage or any other unit.
How to Fix the Issue
To resolve this issue, you need to specify a numeric value for the height attribute instead. If you want the image to occupy a certain percentage of the container, use CSS instead of the height attribute.
Example of Incorrect HTML
Here is an example that causes the validation issue:
<img src="image.jpg" height="100%" alt="Example Image">Corrected HTML Using Pixel Values
To correct the issue, replace the percentage with a pixel value:
<img src="image.jpg" height="200" alt="Example Image">Alternative: Using CSS for Responsive Design
If you want the image to scale responsively and occupy 100% of the width of its container, consider using CSS:
<style>
.responsive-img {
width: 100%;
height: auto; /* Maintains aspect ratio */
}
</style>
<img src="image.jpg" class="responsive-img" alt="Example Image">Summary
- Do not use percentage values for the height attribute of <img> tags.
- Use pixel values for fixed dimensions.
- For responsive design, use CSS to set the dimensions instead.