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Accessibility Score calculation
The accessibility score of a scan is calculated based on the the number of rules violated by the website, and the severity of the rules violated.
Calculating Accessibility score
BrowserStack Accessibility Testing calculates the accessibility score of your website in the following steps:
Based on whether an accessibility rule is applicable, passed, or failed, a multiplier is assigned as follows:
| Multiplier | Condition | Description |
|---|---|---|
| 1 | Passed | The rule is applicable to at least one element on the page. All the elements on the page passed the rule. |
| 2 | Failed | The rule is applicable to at least one element on the page. At least one element on the page failed the rule across page states. Failed rules have a higher multiplier, as failures are penalized more than passes are rewarded. |
| 0 | Not Applicable | The rule does not apply to any element on the page. |
Based on the level of severity of each accessibility rule, a score is assigned as follows:
| Score | Severity |
|---|---|
| 1 | Minor |
| 3 | Moderate |
| 7 | Serious |
| 10 | Critical |
The total actual score and the total possible score are then calculated using the following formulae:
If there are r rules supported by our rule engine, then for every rule i from 1 to r,
For passed rules (1 to p), Impact of passed rules on score = P = Σ(Severityi * Applicablei * Multiplieri)
For failed rules (1 to f), Impact of failed rules on score = F = Σ(Severityi * Applicablei * Multiplierii)
Here, severity mapping is as follows:
Minor: 1, Moderate: 3, Serious: 7, Critical: 10
Note that with the multiplier as 2 for failed rules, the failed rules are penalized twice. This causes the effective value to double as follows:
Minor: 2, Moderate: 6, Serious: 14, Critical: 20
Score (URL & report/scan level) =
Calculate the individual score for each URL that is a part of the report/scan
Accessibility score of a URL or page = P/(P+F)
The page score is calculated using the following formula:
For every page x from 1 to n in the scan,
Accessibility Score (report/scan) = [Σ(Px) / (Σ(Px)+Σ(Fx))] * 100
For an automated test, if the same URL is present across multiple test cases, then:
For every test case from 1 to n,
Total accessibility score for the page at a build level = Σ Passedi / (Σ Passedi + Σ Failedi).
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