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How is the Page and Overall Score calculated in the Eye-Able® Report?

Understanding Scores in the Eye-Able® Report

The Eye-Able® Report includes two types of scores: the page score and the overall score.
Both are based on a weighted points system that considers the severity and frequency of detected accessibility errors, but they differ in calculation method and significance.

Page Score

The page score relates to a single subpage of your domain.
It is calculated by weighting all errors found on that page and combining them into a single score.

The weighting depends on the error’s relevance, based on recommendations from the W3C (World Wide Web Consortium).

Example:

  • A missing alternative text for an image receives a weight of 10, as it is essential for screen reader users.

  • An unnecessarily long caption has a lower weight, e.g., 1.

If an error occurs frequently on one page, its weight can be doubled, highlighting problems that heavily impact that page.

Overall Score

The overall score is not an average of all page scores.
It is calculated independently based on all errors across all tested pages on the domain.

The same weighting rules apply, including the possibility of increased weight for frequently occurring errors.

Key difference:

  • Individual pages might have few error types and thus high scores (e.g., above 90%).

  • The overall score reflects the accessibility of the entire domain.
    → If many different error types appear across pages (e.g., 10 instead of 3), this negatively affects the overall score.

Calculation Formula

Both page and overall scores use logarithmic scaling. The formula is:

logarithmicScaling((sumWeights - sumFailed) / sumWeights)

 

This method ensures that even a few severe errors noticeably lower the score.
Without this scaling, pages with serious issues (e.g., missing form descriptors) could unrealistically achieve high scores.

Conclusion

  • The page score provides information about the condition of a single page and can vary significantly due to localized errors.

  • The overall score reflects the accessibility of the entire domain, considering the variety and frequency of all detected errors.

A high page score does not automatically mean a high overall score – both values should be considered together to get a complete picture.