Cutscenes
Games are a versatile storytelling medium, but make sure you make your cutscenes accessible via voiceovers and captions so everyone can follow along.
Best practices for cutscenes
Any time you need to convey a message to a player, whether that’s through cutscenes, dialog, tutorials, tooltips, or in-game actions and speech, always "say it to the player twice," in two different mediums. That means every message should use both audio AND visual communication.
Cutscene Audio
Voiceovers
Make sure every piece of text in your game has a voiceover. If you don't include audio, you exclude blind players or people with limited vision from understanding your game's story or playing the game altogether.
Terraformers is a game that is completely accessible to the blind because its story, instructions, and mechanics are all narrated by voiceover.
Screenreaders
If recording audio seems too daunting a task, consider adding screen reader compatibility. People with low vision or blindness commonly use screen readers for every day tasks like reading websites and text messages. Screen readers read text out loud using synthesized speech. For Windows, JAWS is the most common screenreader, and it has an extensive scripting language that can be included in your code. Apple's iOS has screen-reading built in too. The Xbox One has a built in narrator, as does the Playstation 4, but they are most often used to navigate menus and not for actual gameplay.
Subtitles
Always Include Subtitles
Make sure every piece of spoken dialog in your game has captions or subtitles. If you don't include text captions, you exclude deaf or hard-of-hearing players from understanding your game's story or playing the game altogether. Also consider people who are playing without headphones or in a noisy environment. Many hearing gamers prefer subtitles too, because they don't want to miss anything in the story.
Five Nights at Freddy's: Sister Location is a bad example because most of the instructions are delivered via voiceover, none of which is subtitled.
Subtitle Formatting
Ideally, you should include the ability to customize caption size in your game's options menu. If this is too cumbersome, make sure you're designing your captions correctly in the first place. Use a readable typeface, like a plain sans serif font, because readers need to be able to quickly read what you have to say. Place your captions within the "safe area" of the interface, not too close to the bottom edge. White text is recommended, but you can use other light colors to denote different speakers. Add a drop shadow or shaded box around text to make it stand out from the background. Subtitles should be two lines or fewer to increase readability. Make sure the line breaks are logical, meaning they don't drop to the next line in the middle of a word or phrase. And finally, the speed shouldn't exceed 160-180 words per minute, but you can also allow players to customize the speed themselves. More on subtitles here and here.
The subtitles in Uncharted 4 are clear and easy to read because they are large, contrast with the background, and display only 1-2 lines at a time. Additionally, a nice typeface adds to the mood rather than distracting from it.