ALT Text Icon
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**Describe the requested icon(s)**

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I would like to see an icon with the letters ALT surrounded in a single line box to represent the availability of alternate text on a media file. For example, these often show up on images, video and audio attached to social media posts. It should match closely to the CC icon that already exists, the only change would be the letters ALT instead of CC.

CC stands for Closed Captioning, so it's not quite the same thing as ALT text, which is a description of the media file itseld, not dialog in a video.

[ALT text](https://www.section508.gov/training/alt-text/what-is-alternative-text/) is useful for everyone, as a way to further classify media and as an alternative for those with low sight that are using text readers. Having an icon specific to this need would be helpful.

You may also want to include a version with a slash through it, representing media that do NOT have ALT text attached. This is similar to a representation you have now with the `subtitles` and `subtitles-slash` icons.

The names for the icons could be `alt-text` and `alt-text-slash`

**References**

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![Image](https://github.com/user-attachments/assets/7a9da050-f884-4a03-ade5-154128876665)

![Image](https://github.com/user-attachments/assets/44d3d61e-5634-4765-859e-12f30c8fa90a)

![Image](https://github.com/user-attachments/assets/a1baac0d-1339-4e90-9d0c-a88a662fa223)

**Additional context**

The term ALT is widely used and understood across most platforms and would be an excellent addition to the library. Additionally, you have very similar items in the library already, so it should be fairly easy to create this from the existing cc and subtitles icons.

Thanks for your consideration!

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