Embedded Files
Grackle is an extension for Google Workspace that checks documents, slides, and sheets for barriers to accessibility and provides guidance for improvements.
The Grackle extension is powerful because it can be used to increase the accessibility of materials beyond what can be implemented manually in Google Workspace apps.
Grackle can be helpful as a checker, but it is not a substitute for understanding accessibility best practices. Improving accessibility still requires discretion, and the warnings and instructions provided by Grackle may be difficult to interpret without prior knowledge of accessibility practices.
This guide offers a more detailed explanation of the checks that Grackle performs and the options for addressing the issues it identifies.
Using Grackle Slides
Using Grackle Slides
Running an Accessibility Check
Running an Accessibility Check
To install:
Open a slide deck in Google Slides
Select "Extensions →Add-ons → Get add-ons"
Search for Grackle Slides and select "Install".
Grackle needs to be installed separately in each app (Slides, Docs, Sheets).
To run a check:
Select "Extensions → Grackle Slides → Launch"
Give permission for Grackle to access and change your files (you may be asked to re-authorize whenever you launch Grackle)
Grackle Docs will open in the right sidebar (highlighted in image at right) and run a check.
Understanding the Checks
Understanding the Checks
Grackle will check for 16 items, grouped into 5 sections. Each item will be assigned either a:
Green checkmark = Pass
Green checkmark with an exclamation = Warning
Red X = Fail
The "Warning" label is particularly hard to interpret. Sometimes it is given when an issue may not a problem in context (which requires your discretion to decide), but sometimes it is given when issues should almost certainly be fixed and thus "fail" would be the more appropriate label.
The Pass label is also sometimes given in cases where an accessibility barrier clearly exists. For this reason, it is best to review the whole checklist, even the items that receive a Pass. The sections below describe each check and identify when Grackle's labeling is counterintuitive or unreliable.
Presentation Section (2 checks)
Presentation Section (2 checks)
❌ Presentation title is required
❌ Presentation title is required
Presentations should have a title, and a single title slide. The Presentation Title will, by default, be the name of the file.
Caveats
Pass = This check will pass even if your file is called, “Untitled presentation,” so it’s fairly meaningless.
Warning = Grackle will list the slides that use the "Title slide" layout and give a warning if more than one title slide is found. The presentation should only have one "Title slide," (even though these titles are not considered the presentation title) so the layout of other slides should be changed using the slide editor (cannot be edited through the Grackle sidebar).
Fix (Optional): To give the presentation a title that is different from the file name,
Select the Grackle blue button “Edit Title”
Change the title in the Properties window (this Properties window is only available though Grackle)
❌ Document language should be specified
❌ Document language should be specified
This is a behind-the-scenes specification that is different from your Google Slides language (which is set under File → Language). It’s not clear how these two language settings interact.
Caveats
Fail = This check will fail if the language is not set in Properties, which is only available to edit through Grackle
Fix:
Select the Grackle blue button “Set Language”
In the Properties window, select “en” under Language for english
Select “Update” at the bottom of the window.
Slides Section (3 checks)
Slides Section (3 checks)
❌ A slide should have a title
❌ A slide should have a title
Titles improve navigation for all and allow users of adaptive technologies to scan the list of slides and find slides without having to go through the entire presentation. For technologies to recognize titles, they must be in specific title placeholder boxes, which can only be inserted at the layout/theme level.
Caveats
Warning = You may get a Warning instead of a Fail even if Grackle identifies missing titles.
Grackle will provide the numbers of slides with missing or empty titles: "Some slides may need titles: Slide 3"
Fix, Option 1: Change to a slide layout that includes a title placeholder (the slide starts with a text box that reads “Click to add title”)
Select a layout to apply under “Layout” in the editing ribbon or by right-clicking the slide and selecting “Apply Layout”. Choose a layout that contains a title placeholder.
If the slide you are fixing has a lot of elements, you might find it easier to add a new slide, apply a layout with a title, and then copy the original slide text over into your new slide.
Fix, Option 2: Edit the layouts in your presentation to add title placeholders to layouts missing titles
Under “Slide” in the top menu, select “Edit theme”
Select the layout you want to edit from the left-hand menu within the theme-editing window (dark background) For example, select the Blank layout to add a title to all slides in your presentation using the Blank layout.
Select “Tt” (“Insert text placeholder”) from editing ribbon (pictured below)
Select Title placeholder. Move the placeholder to where you want it on the slide.
Close the theme-editing window.
❌ Slide title should be unique
❌ Slide title should be unique
If multiple slides cover content on the same topic, add numbers (e.g. “Resources 1” or “Resources: Part 1 of 3”) or terms like “continued” so people can differentiate and perceive the order of slides.
Caveats
Pass = You may get a Pass instead of a Fail when slides are missing titles completely.
Fix:
Change title text on the slide. Add numbers (e.g. “Resources 1” or “Resources: Part 1 of 3”) or terms like “continued” (e.g., “Resources, continued”) when multiple slides cover content on the same topic.
❌ A slide should not be empty
❌ A slide should not be empty
A completely empty slide is a little confusing, as users of adaptive technologies may wonder if the slide contains content that they are missing.
Caveats
Pass = This check will fail only if a slide is completely free of elements. It will pass if the slide has nothing but empty textboxes, even though this is equally a problem. A different check in the Elements section will fail if there are empty textboxes.
Fix:
Avoid using completely blank slides. To create a moment where nothing is being presented, set text objects on the following slide to appear on click, so that the slide appears blank when you first advance to the slide.
Tables Section (3 checks)
Tables Section (3 checks)
❌ Tables should be tagged and described
❌ Tables should be tagged and described
Tables create a number of access issues. Adaptive technologies that allow users to change formatting may not work with tables. Screen readers will read out every cell in left-to-right, top-to-bottom order, which is difficult to interpret.
Avoid the use of tables for layout, but if using a table for layout, tag (label) it as a layout table to let users know that there is no relationship between the rows and columns. Using the Grackle red button “+TAG” is currently the only way to add these tags to tables in Slides.
For data tables, tag (label) the header rows and columns to give users a way of understanding the relationship between cells in the table. Using the Grackle red button “+TAG” is currently the only way to add these tags to tables in Slides.
Add a summarizing description to the table so users can understand what the table contains. This is similar to alt text for images; in Google Slides, tables have an alt text field where this description can go.
Caveats
Pass = You may get a Pass instead of a Fail even if there is no alt text description. There is a different check in the Elements section that will fail when a table has no alt text.
Fix - Tags:
Select the Grackle red button “+TAG” to open the Tag Table window.
Check one of the boxes at the top of the window (above where an image of your table is displayed; picture below)
Check “Table is used for layout only” if it is not a data table
Check “Mark first row as header” if the first row contains labels for the columns
Check “Mark first column as header” if the first column contains labels for the rows
The checkboxes underneath the table image are for labeling individual cells (for a complex table layout; for a standard data table, these can be ignored)
Select “Update” in the borrow right of the window
Fix - Description:
Right-click the table and select “Format options”
Select “Alt Text”
In the text box, describe the significant data or trends that the table displays
❌ The use of merged cells is not recommended
❌ The use of merged cells is not recommended
Merged cells will cause screen readers to lose track of cells’ locations in the table. Avoid merged cells in a data table. When a table is used for layout, this no longer matters.
Fix:
1. Manually unmerge cells by right-clicking the cell and selecting “Unmerge”
❌ The use of empty cells is not recommended
❌ The use of empty cells is not recommended
Empty cells can be confusing. Users of adaptive technologies may think that there is no more data or that they are missing content.
Fix:
1. Avoid having empty cells. Add placeholder content (e.g, “NA” or “none”) to cells that don’t have values.
Elements Section (4 checks)
Elements Section (4 checks)
❌ Images should have alternative text
❌ Images should have alternative text
Provide text alternatives for any non-text content (photo, illustration, chart, graph, table, infographic) so that it can be changed into other forms people need. If an image is pure decoration or is used only for visual formatting, mark it as an artifact or decorative so it can be ignored by adaptive technologies. This can only be done through Grackle.
Fix:
Select the Grackle green button “+TAG”
In the text box, describe the image. Use a short phrase (unless the image conveys complex information) that reflects the essential content/purpose of the image. Do not begin with "Image of" or "Picture of" and avoid repeating information that is already included in the surrounding text.
If the image does not convey meaning and is only for visual styling, select “Mark as artifact”
Select “Update”
You can also access and edit the alt text by right-clicking the image and selecting “Format options.” The alt text will be shared between these two places. However, using the Grackle button is the only way to mark an image an an artifact (decorative)
❌ Elements should have alternative text
❌ Elements should have alternative text
All non-text content needs text alternatives so it can be changed into other forms people need. Grackle runs separate checks for images and other non-text elements (shapes, diagrams, charts, tables).
Fix:
Select the Grackle green button “+TAG”
In the text box, describe the image. Use a short phrase (unless the image conveys complex information) that reflects the essential content/purpose of the image. Do not begin with "Image of" or "Picture of" and avoid repeating information that is already included in the surrounding text.
If the image does not convey meaning and is only for visual styling, select “Mark as artifact”
Select “Update”
You can also access and edit the alt text by right-clicking the image and selecting “Format options.” The alt text will be shared between these two places. However, using the Grackle button is the only way to mark an image an an artifact (decorative)
❌ Text boxes should not be empty
❌ Text boxes should not be empty
Empty textboxes can be confusing. Users of adaptive technologies may think that they are missing content.
Fix
Add text or delete empty text boxes
❌ Lists should not be broken apart
❌ Lists should not be broken apart
Creating lists using the options in the formatting menu (rather than by hand) allow users of adaptive technologies to understand the order and navigate through list items. This navigation is disrupted if extra lines or other formatting separate items in a list.
Caveats
This check applies to numbered lists only. This issue is less relevant for unordered (bullet pointed) lists.
Pass = This check will not check manually formatted lists. These need to be found and reformatted by you.
Fix:
Use list formatting. Keep formatting consistent between numbered list items and don’t separate them in space.
Contents Section (4 checks)
Contents Section (4 checks)
❌ Fine print should be avoided
❌ Fine print should be avoided
Recommendations for accessible minimum font size vary. Grackle will pass font sizes of 9pt and larger; more typical recommendations are 18pt or even 24pt for body text. But this depends on context, such as how far away users will be from the presentation, and is much less important when slides are digitally shared.
Caveats
Warning = You may get a Warning instead of a Fail even if Grackle identifies small fonts.
Fix:
Change font size for any text that you want audience members in a live presentation to be able to read to be at least 18pt.
❌ High color contrast should be used
❌ High color contrast should be used
High color contrast makes it easier to read text and distinguish between elements on the page. Learn more about color contrast.
Caveats
Warning = You may get a Warning (check with exclamation mark) instead of a Fail even if Grackle identifies low contrast.
Fix:
Use the WebAIM Contrast Checker to ensure background and foreground colors are significantly different from each other (look for the green "Pass" label").
For simplicity, use the first row of pastel colors on Google Slides if you need a background color for black text.
❌ In-line style changes may lack clear meaning
❌ In-line style changes may lack clear meaning
This check identifies text formatting differences within a text box, such as bolded words. These formatting changes are often fine, just keep in mind that users of adaptive technologies will not have access to those visual cues.
Fix:
Avoid using formatting as the only way of communicating information (for example, using font color only to differentiate between item categories).
Use bold for emphasis when possible, rather than italics and all-caps, which are harder to read.
❌ Empty trailing lines could be removed
❌ Empty trailing lines could be removed
This check identifies extra space at the end of text boxes (i.e., if you hit down at the end of a paragraph or list, the cursor will go down into the empty space). Some adaptive technologies may read that there is something empty there, which can be confusing, but this is a very minor issue.
Fix:
Delete empty lines after paragraphs and list items. Use line and paragraph spacing to create space between sections of text.
Using the Slides Structure Tab to Correct Reading Order
Using the Slides Structure Tab to Correct Reading Order
Slide components (like text boxes) will be read by adaptive technologies in an order that may be different from the order you intend or the order implied by physical position. The reading order of each slide needs to be checked and corrected.
Reading order is visible under the tab “Slides Structure”, next to the tab for “Accessibility Check.” Grackle does not know whether the reading order is correct; this must be manually checked. This tab allows you to see the reading order and drag slide components to reorder them.
The “Failure” labels in the Slides Structure tab have no clear or consistent meaning and should be ignored. For example, it may label every component as “Failure,” but if you recheck when Slides Structure is open, all of the failures disappear.
Fix:
Select the Grackle Slides Structure tab.
For each slide, the slide components are listed in the order they will be read. If you can’t tell what a component name refers to, select the component name to highlight it in the slide.
Drag components in the list put them in a logical order.
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