You can install Grackle Sheets here.
When opened, it scans the current Sheet (all tabs) for accessibility issues.
When the scan finishes, Grackle Sheets arranges the document’s elements and structures into 4 categories.
These categories can be seen in the user interface on the right side of the screen.
Elements in each are marked as either accessible or inaccessible. Changes are made by selecting and editing these elements in these categories. For example, a table does not have the header row specified with a tag.
Sheets properties are important for ensuring the document is not too unwieldy.
Tables within work sheets are commonly inaccessible.
They pose a special challenge for screen readers because they present textual or numerical data to be easily referenced visually.
Once Grackled, this grid turns into a fully functioning, marked up table which can be output to Accessible HTML.
Grackle checks to ensure any charts that have been embedded contain alt-text
Grackle scans against and helps resolve two content-related accessibility issues.