Add alt text on every platform

At a glance

Limits are what the field accepts today, and platforms change them without notice. Treat them as room to work in, not targets to fill.

Instagram & Threads

1. Create your post and pick your photo, then advance to the final screen (the one with the caption box).
2. Tap Advanced settings at the bottom.
3. Under Accessibility, tap Write alt text.
4. Type your description and tap Done, then share.

Already posted? On Instagram, open the post → ⋯ → Edit → tap the photo → Edit alt text. Threads follows the same flow at post time.

Facebook

1. Start a post and add your photo.
2. Hover the image and click the Edit (pencil) icon.
3. Choose Alternative text in the left panel.
4. Click Override generated alt text, type your description, and Save.

To fix a live post: open it → ⋯ → Edit post → pencil on the image → Alternative text.

X (Twitter)

1. Compose a post and attach your image or GIF.
2. Click the ALT badge in the corner of the image preview.
3. Write your description in Describe this image… and click Save.
4. The badge turns bold to confirm alt text is attached. Post as normal.

Do it before you post. X does not let you add or edit alt text after publishing.

LinkedIn

1. Start a post and upload your image.
2. Click Alt text (bottom-right of the image editor).
3. Enter your description and click Save, then post.

You can fix LinkedIn alt text after posting, but only on the desktop site. Open the post, use the three dot menu, choose Edit post, then Edit on the image. The mobile app has no way to do it, and sources disagree on whether the desktop route always works, so the safe habit is still to check before you publish.

TikTok

1. Upload a photo post and continue to the final screen.
2. Tap More options.
3. Tap Advanced settings → Add alt text.
4. Type your description and confirm, then post.

Alt text applies to photo posts. For video, rely on captions and on-screen/spoken description instead.

Bluesky

1. Compose a post and add your image (or video).
2. Tap + ALT on the media thumbnail.
3. Write your description and save.

In Settings → Accessibility, turn on Require alt text so Bluesky reminds you before you can post without it.

Mastodon

1. Compose a post and attach media.
2. Click Edit / ALT on the attachment.
3. Write your description in Describe for people who are blind or have low vision and click Apply.

You can edit a post (and its alt text) after publishing, but note that boosting carries the original description, so get it right at the source.

Pinterest

1. Create a Pin and upload your image.
2. Open the Pin's ⋯ menu → Edit Pin (or scroll to the alt-text field while creating).
3. Fill in the Alt text field and save.

YouTube

YouTube has no alt-text field. Accessibility comes from a descriptive title, a thorough description, accurate captions, and audio description for anything shown but not said. See captions & audio description.

Limitations & gotchas

Even when a platform offers alt text, the feature has real limits worth planning around:

• Length pressure forces compromises. WCAG says describe as much as the image needs. The Meta apps do not hard stop you, but they warn once you pass about 100 characters, and several other platforms publish no limit at all. Treat 100 as the working budget everywhere. When space is tight, put the essential meaning in the alt and the rest in the visible caption.
• Some platforms lock alt text after posting. On X and TikTok you cannot fix a description later at all. LinkedIn lets you, but only from the desktop site. Proofread before you publish and none of this matters.
• Auto-generated alt is unreliable. Meta's AI alt ("Image may contain: tree, sky") is a fallback, not a description. Always override it.
• Video usually has no alt field. Alt text is for still images. Video accessibility comes from captions, transcripts and audio description instead.
• Reshares and reposts can drop alt text. A quote-post, screenshot or cross-post often loses the original description, so re-add it.
• Schedulers vary, and Meta took the feature away. As of April 2026 you can no longer add alt text through Meta Business Suite at all, so anything scheduled there goes out with Meta's auto-generated guess or nothing. Many third-party tools drop it too. Check your tool, or add the alt natively afterwards.
• Alt text isn't a keyword box. Don't stuff hashtags or repeated phrases in, because screen-reader users hear every word.
• Screenshots have no alt. Text baked into an image can't be read, so keep important words as real post text.