CSS Lint

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Errors
Compatibility
Performance
Maintainability & Duplication
OOCSS
Accessibility
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Want to check your CSS code from Pro?

CSS Lint is a free online tool that helps you point out the problems in your CSS code. It is a primary syntax validation tool that implements rules that look at the problematic patterns and signs of inefficiency in your CSS code. In CSS lint, performance optimization, error correction, OOCSS, compatibility checking can be performed to make your CSS code more efficient.

What exactly is a Lint?

According to Wikipedia, Lint (software) means
Lint or linter is a code analysis tool that flags programming errors, like bugs, stylistic mistakes, and suspicious constructs and its questionable usage in software or program written in any computer language.
Therefore, lint is a performance checker. That checks the problematic patterns in your code that brings the inefficiency.

Why is CSS Lint important?

No doubt, it is challenging to do the coding because a little mistake in your code can affect the whole performance of your code. Just writing code is not enough. However, writing CSS code in such a way that it is error-free, and efficient is of utmost importance.
We learn from our mistakes. No one can become the “ Mentor" at the start in its field. Talking about any area of life, we have to start from the basics. With time, by facing new problems, challenges, we learn from our mistakes, and after some time, we achieve perfection.
The same goes for the field of programming. Getting checked your program from a "Pro" or your "Senior" or "Mentor" is a great way to improve your programming skills. However, if that facility is not available, you can use the lint for that language.
Performance cannot be sacrificed at any cost. CSS lint is a tool for checking the CSS performance of the browser. CSS lint performs the CSS code's basic syntax checking to point out your CSS code's problems.
That is required in an established organization where you work on big projects like mammoth type project with a team full of skilled developers. Moreover, you are required to optimize the page performance to the level where that tool aims to take.

The CSS Lint Rules

Nicholas Zakas and Nicole Sullivan create the CSS Link. That applies some set of rules on the code to find the signs of problematic patterns that cause inefficiency.
That rules are divided into Errors, Maintainability, and Duplication, Compatibility, OOCSS, Performance, and Accessibility sections.
Errors

  • Beware of broken box-sizing.
  • Require properties appropriate for.
  • Disallow duplicate properties.
  • Disallow empty rules.
  • Require the use of known properties.
Maintainability and Duplication
  • Disallow too many floats.
  • Do not use too many font sizes.
  • Disallow IDs in selectors.
  • Disallow !important.
Compatibility
  • Disallow adjoining classes
  • Disallow box-sizing.
  • Require compatible vendor prefixes.
  • Require all gradient definitions.
  • Disallow negative text-indent.
  • Require standard property with the vendor prefix.
  • Require fallback colors.
  • Disallow star hack.
  • Disallow underscore hack.
  • Bullet-proof @font-face.
OOCSS
  • Disallow qualified headings.
  • Heading should only be defined once.
Performance
  • Do not use too many web fonts.
  • Disallow @import.
  • Disallow duplicate background images.
  • Disallow selectors that look like regex.
  • Disallow universal selector.
  • Disallow unqualified attribute selectors.
  • Disallow units for 0 values.
  • Disallow overqualified elements.
  • Require shorthand properties.
Accessibility
  • Disallow outline: none.
Note How many rules you want to apply, it depends upon you. These rules are pluggable. If you are going to use all the rules, you can select all rules or omit some you do not want to apply.

How to use the CSS Lint tool?

Use the CSS Lint tool for performance optimization, error correction, OOCSS, and compatibility checking to make your CSS code more efficient and problem-free. You must perform the following steps.

  • Open the CSS Lint tool.
  • You can copy-paste the CSS code or use the "Load From URL" or "Browse" option to upload it.
  • After uploading the code, select the "rules" from the checklist that you want to apply. If you wish to use all rules, check all the rules. If you are going to involve some specific rules, you can apply those rules as well. It depends on you.
  • After selecting the rules, click on the "Convert" button.
  • The tool will provide you the results if it finds any problem.

How to use the "Load Sample Data" option in the CSS lint tool?

Before using any online tool, it is always better to first load some sample data to check that tool's working. To see whether that tool is performing and giving you results as per your requirements.

  • To use this, do the following steps.
  • Click on the "Load Sample Data" option to upload the sample data.
  • Select the "rules" from the checklist to apply to the code.
  • Click on the "Convert" button to get the results.

Should we use CSS lint?

The answer is, "yes." Because CSS lint helps you in basic syntax checking and points out your code's problems, make your code more efficient. You may have some questions or doubts about some rules. However, these rules are pluggable; if you want to omit specific rules, you can do that.
Also try our CSS Beautifier online tool and CSS Minifier online tool for productivity improvement.

Do we keep a copy of your source code?

Protecting user trust is our top priority. We do not keep a copy of the source code that the user input or upload for the CSS lint process.