I've used tools like UsableNet to scan for WCAG 2.1 Level AA (and tools like Siteimprove to check for things like reading age levels for text), but now I'm looking to go a step further and scan for issues as part of WCAG 2.1 Level AAA. However, I haven't found any tools/services that do that.
I did come across this: https://tetralogical.com/blog/2021/12/09/testing-wcag-level-aaa/
And it says:
Most tools available for automated or manual testing only cover Level A and Level AA criteria.
My one bit of hope is that is says "most tools" and not "all tools".
Is there a tool/service that will scan for and surface the level AAA issues (either on a specific webpage or an entire website)?
The W3C has a list of accessibility tools on https://www.w3.org/WAI/ER/tools/. There are currently 166 tools listed, so plenty to pick from. They have some filters but one of them is not by WCAG level so you can't view just AAA tools. But doing a simple text search of "AAA" on the page shows a few.
Update, based on comment:
Unfortunately, the tool you picked looks like an "overlay", which purports to fix your website with "one line of code" (their marketing line, https://www.equally.ai/interface). There is 0% chance that a tool can fix all accessibility issues. Fixing accessibility issues requires a human being. Finding accessibility issues requires a human being.
Scanning tools help find accessibility issues, although all results from a scanning tool must be scrutinized for false positives. Do not assume scanning tool results of infallible, even if the tool comes from a reputable company.
A lot of WCAG is very subjective and it's impossible to build a tool that can make subjective decisions.
For example, WCAG 2.4.6 Headings and Labels
"Headings and labels describe topic or purpose."
Can a tool decide if a heading (<h1>, <h2>, etc) or a label (<label>, aria-label) describes the element sufficiently? Absolutely not. There's no way a tool can analyze the content of a section and then decide if the heading accurately describes that section.
So if a tool cannot detect if a heading or label is descriptive or not, how can a tool fix those issues with "one line of code"?
What about an easier guideline? WCAG 1.1.1 Non-text Content
"All non-text content that is presented to the user has a text alternative that serves the equivalent purpose, except for the situations listed below..."
Most scanning tools use a simple interpretation of that guideline and say that <img> elements must have an alt attribute. The HTML spec regarding the alt text is a bit more complicated.
However, let's say the tool uses the simple interpretation. Can a tool scan for all <img> elements and see if the alt attributes exists? Absolutely. Can it warn you that it's missing? Absolutely, although it should be a warning and not an error since as mentioned in the spec, there are cases where you don't need alt.
Can a tool decide if an image is decorative or informative? That is, can the value of alt be an empty string, "", or have a null value, or should it describe the image? No way.
So if a tool can't figure that out, how can a tool fix your images? What is it going to inject as a description of the image?
Sorry for the long diatribe here. Scanning tools can be quite helpful in finding accessibility issues but scanning tools are very limited in what they can find. Good scanning tools can find maybe 20% of your accessibility issues. What about the other potential 80% of issues that might exist? That requires a human being - one well-versed in testing for accessibility.
So if a scanning tool has very limited success, do you think a tool can exist to actually fix accessibility issues?
Feel free to use the tool you chose to scan for issues so that you can fix your code. But do not rely on a tool to magically fix issues for you, especially when they charge a monthly subscription to do so.
Here are some other articles regarding "overlay" tools, which again are tools that purport to automatically fix issues for you: