How Does the W3C Recommend Quoting URL Values in CSS's `background-image` Property?

Quoting url() Value: A W3C Perspective

In CSS, the background-image property utilizes the url() function to specify an image source. While there are multiple ways to define the URL, including using single or double quotes or omitting them altogether, what does the W3C recommend?

W3C Standard

According to the W3C, quoting the url() value is optional. All the provided examples are considered valid:

• background-image: url(image.png);
• background-image: url("image.png");
• background-image: url('image.png');

Consistency and Special Characters

However, the W3C emphasizes that if both opening and closing quotes are used, they must be the same character.

Additionally, if the URL contains special characters like parentheses, white space, or quotes, quoting is recommended to prevent any unintended behavior. Special characters can be escaped with a backslash, but quoting is generally preferred.

Syntax

The syntax for a URI value in url() is defined as:

'url(' followed by optional white space
followed by an optional single quote (') or double quote (") character
followed by the URI itself
followed by an optional single quote (') or double quote (") character
followed by optional white space
followed by ')'

The two quote characters must be the same.

Conclusion

While quoting the url() value is not mandatory, it ensures consistency and correct handling of special characters. By following the W3C recommendations, developers can enhance the reliability and maintainability of their CSS code.

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