Do I need to add CC if all text is on screen?

You should add CCs I believe WCAG 2.1 requires all videos to have captions

Hi Lorraine and welcome to the community!

This question is tricky because the WCAG (Web Content Accessibility Guidelines) are written to make all web content more accessible, but they tend to be framed specifically around how websites function. Since e-learning is a related but different medium, sometimes it takes a bit of work to figure out how a specific guideline applies in our world.

The WCAG for captions on prerecorded content states: Captions are provided for all prerecorded audio content in synchronized media, except when the media is a media alternative for text and is clearly labeled as such.

So in most cases, a Storyline course with audio narration requires captions to be accessible. But you mentioned your course also has the narrated content on screen as text. In that case, the "...except when the media is a media alternative for text and is clearly labeled as such." part of the standard may apply.

Thankfully, the organization that created these standards also made a site that digs deeper into how they apply in real-world situations. And their page on this guideline mentions "Captions are not needed when the synchronized media is, itself, an alternate presentation of information that is also presented via text on the Web page."

Based on that advice, if your on-screen text and audio narration cover the exact same information in the same way, it sounds like captions wouldn't be needed since the on-screen text covers the exact same purpose for learners. However, if the audio and on-screen text differ in any way, you'd want to adjust the on-screen text or add captions. Full transparency, though, that I'm not a WCAG expert and someone who is may have more insight on how this is meant to be interpreted.

Side thought: it's not mentioned in the guidelines, but If you leave off captions you may want to add a note to the course (or the course description on your LMS) mentioning that all audio content is also included as onscreen text. That way learners who typically depend on captions will know they aren't missing out on anything.