Definition of Yslow
Interpret results and improve scores
When the desired web page is searched, it is compared against a list of 23 rules. These rules are based on Yahoo’s “high performing websites”. The open source tool next evaluates the web page against these 23 rules and returns an overall score based on this average.
Each of the 23 rules has a different weighting. That is, some rules have a greater impact on the overall score than others. For example, limiting the number of HTTP requests made by the web page has a greater impact on the score than decreasing the size of the Cookies.
When the web page is run through GTmetrix, all the results and information can be viewed. First, you see an overall score. This is again the weighted average of the performance of the web page compared to all 23 rules.
The total score works just like the tests in school: 100% is a perfect score and 0% is the worst possible score.
Displaying the individual rules
Ultimately, all that is offered is a set of suggestions to improve the performance of the front-end elements. These suggestions are valuable and can help with optimization.
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