Social media is visual by design. Photos, screenshots, infographics, and memes drive engagement across every platform. But when you skip alt text, you shut out people who use screen readers from the conversation.
Alt text on social media is not just a checkbox for compliance. It is how you make your content accessible to blind and low-vision users, it helps people on slow connections, and on some platforms it makes your posts easier to find. This guide covers platform-specific best practices for Bluesky, LinkedIn, and Instagram so you can write alt text that actually works.
Why Social Media Alt Text Is Different
Alt text on social platforms serves the same core purpose as alt text on the web, but the context changes how you should write it.
Social posts are conversational. Your alt text should match the tone of your post. If you're joking, the alt text can be casual. If you're sharing professional insights, keep it professional.
Context matters more. The same photo needs different alt text depending on your caption. A sunset photo on a travel account might focus on location details. The same sunset in a motivational post needs alt text that supports the message.
Character limits vary. Bluesky allows 2,000 characters and X allows 1,000, while LinkedIn, Instagram, and Facebook publish no limit for the field in their apps. Our list of alt text character limits has each one with its source, checked October 2026.
Screenshots and text-heavy images are common. Social media is full of posts, messages, and text graphics. Your alt text must include the visible text that matters for screen reader users.
Best Practices for Bluesky
Bluesky allows up to 2,000 characters of alt text and makes it easy to add while you write your post.
How to Add Alt Text on Bluesky
When composing a post with an image, select ALT on the image thumbnail. A dialog opens with a field for your description. Write it and select Save. Bluesky cannot add alt text to a post after it is published, so add it before you post. Under Settings, then Accessibility, you can turn on Require alt text before posting as a reminder.
Bluesky Alt Text Best Practices
Match your post's tone. Bluesky culture is conversational and informal. Your alt text can be too.
Example post: "just planted my first garden and i'm unreasonably proud of these tomatoes"
Alt text: "Hands holding three large red tomatoes in a backyard garden with raised beds visible in background"
Include text from screenshots. Bluesky is full of screenshot threads. The words in the screenshot need to be in your alt text.
Example: Screenshot of a post
Alt text: "Post from @username: 'The problem with debugging is that you have to understand the code you wrote six months ago when you were a different person.'"
Describe memes completely. Meme formats are visual jokes. Describe both the image structure and the text overlays.
Example: Distracted boyfriend meme
Alt text: "Distracted boyfriend meme. Man in red shirt looking back at woman in red dress while his girlfriend in blue looks annoyed. Top text: 'Me.' Woman he's looking at: 'Starting a new project.' Girlfriend: 'Finishing my existing projects.'"
Keep context from your caption in mind. If your post already describes what's happening, use alt text to add details, not repeat yourself.
Post caption: "New coffee shop opened downtown with the best matcha latte I've ever had"
Alt text: "Green matcha latte with latte art in white ceramic cup on wooden table, natural light from window visible"
Best Practices for LinkedIn
LinkedIn does not publish a limit for the alt text field in its app. Its developer documentation allows up to 4,086 characters and recommends staying under 120. Professional context means your descriptions should be clear and informative.
How to Add Alt Text on LinkedIn
According to LinkedIn's help article, after uploading an image on desktop, click Alt. text below the image, write the description, and click Save. In the mobile app, tap ALT below the image and tap Done. LinkedIn may add alt text automatically when you don't, so it is worth replacing it with your own.
LinkedIn Alt Text Best Practices
Be professional and specific. LinkedIn is a professional network. Your alt text should reflect that.
Example: Photo at a conference
Alt text: "Three software engineers reviewing code on laptop at Tech Summit 2024, conference badges visible"
Describe charts and data visualizations clearly. LinkedIn posts often include graphs and metrics. State the key insight, not every data point. Our guide to alt text for charts and graphs has more examples.
Example: Bar chart showing growth
Alt text: "Bar chart showing quarterly revenue growth from Q1 to Q4 2024, increasing from $2M to $5.5M"
Include visible text from slides and presentations. If you're sharing presentation screenshots, include the slide title and key bullet points.
Example: Presentation slide
Alt text: "Slide titled 'Q4 Strategy Priorities' with three bullet points: Expand enterprise sales team, Launch mobile app beta, Improve customer onboarding experience"
Add context for headshots and team photos. Identify people when relevant, describe professional settings.
Example: Team photo
Alt text: "Marketing team of six people standing in modern office space, floor-to-ceiling windows with city view in background"
Don't repeat your post caption verbatim. If your caption says "Excited to share our new product launch," your alt text should describe the product image, not announce excitement.
Best Practices for Instagram
Instagram does not publish a limit for alt text in its app, and it fills in automatic alt text from object recognition when you don't write your own. Automatic alt text can name what it detects, but it can't know why you posted the image.
How to Add Alt Text on Instagram
The steps are from Instagram's help article.
When creating a post in the app: After selecting your photo and editing it, tap Next, then More options. Tap Write alt text, enter your description, and tap Done.
For existing posts: Go to the post, tap the options menu, tap Edit, then Edit alt text in the bottom right.
Instagram Alt Text Best Practices
Keep it short and specific. Instagram's alt text is only read by screen readers, so every word should help someone who can't see the photo.
Example: Product photo
Good: "Woman wearing oversized cream sweater and black jeans, sitting on gray sofa"
Bad: "Beautiful lifestyle shot of a woman modeling our new fall collection in a modern minimalist living room with natural light"
Focus on the visual, not the vibe. Describe what's in the image, not the feeling you want it to convey.
Vague: "Cozy autumn aesthetic"
Specific: "Pumpkin spice latte with cinnamon stick on wooden table with fall leaves"
Describe the image, not the emoji in your caption. If the caption leans on emoji to set the mood, the alt text still needs to say what the photo shows.
Post caption: "New studio space" followed by sparkle and palette emoji
Alt text: "Bright art studio with paint-covered easel, canvases stacked against white wall, skylight overhead"
Don't over-describe aesthetic photos. Instagram leans heavily on mood and style. Focus on concrete details, not abstract interpretations.
Unnecessary: "Ethereal morning light creating a dreamlike atmosphere"
Better: "Empty beach at sunrise, pink and orange sky reflected in wet sand"
Include text from graphics. Instagram is full of quote graphics and infographics. Screen reader users need access to that text.
Example: Motivational quote graphic
Alt text: "Beige background with black text reading: 'Progress over perfection'"
Common Mistakes to Avoid on Social Media
Using Generic Descriptions
"Image" or "photo" tells screen reader users nothing. Be specific.
Bad: "Image"
Good: "Chocolate chip cookies cooling on wire rack"
Starting with "Image of" or "Photo of"
Screen readers already announce it's an image. Don't waste characters.
Unnecessary: "Image of sunset over ocean"
Better: "Sunset over ocean with orange and pink clouds"
Describing Feelings Instead of Facts
Alt text should describe what's visible, not how you want people to feel about it.
Vague: "Inspiring workspace"
Specific: "Standing desk with dual monitors, succulent plant, and notebook"
Skipping Text from Screenshots
If your image has text that matters, that text belongs in the alt text. Our guide to alt text for screenshots covers long text and message threads.
Writing Alt Text for the Algorithm
Don't stuff keywords into alt text hoping for better reach. Write for humans using screen readers.
Bad: "Coffee morning coffee latte art best coffee shop coffee beans artisan coffee"
Good: "Cappuccino with leaf latte art pattern in white cup"
Platform Comparison: Alt Text Features
As of October 2026. Sources for each limit are in our alt text character limits list.
| Platform | Alt text limit | Automatic alt text |
|---|---|---|
| Bluesky | 2,000 characters | No |
| Mastodon | 10,000 from version 4.6, 1,500 on older servers | No |
| Not published for the app | Sometimes | |
| Not published for the app | Yes | |
| Not published | Yes |
For step-by-step instructions on all six, see how to add alt text on social media.
How AltKit Helps with Social Media Alt Text
Writing thoughtful alt text for every post takes time. AltKit gives you a draft to start from:
- In your posting flow. The browser extension adds a Create Alt Text button to the alt text dialog on Bluesky, X, Mastodon, LinkedIn, Instagram, and Facebook, and writes the description into the field.
- Written for social posts. Plain sentences, usually two or three for a photo, and never longer than 1,000 characters.
- Reads the words in the image. Meaningful text in screenshots, memes, and graphics is quoted exactly.
AltKit is free. A free account comes with a daily allowance of images across the web app and the extension, and with your own AI provider key the extension has no daily limit. See free use and the daily limit for the details.
The Bottom Line
Alt text on social media isn't optional. Every image without alt text excludes someone from the conversation.
Bluesky gives you space to be descriptive. LinkedIn expects professionalism and clarity. Instagram rewards brevity. But the core principle stays the same: describe what's visible in a way that makes sense for screen reader users.
You can write it yourself, or start from an AltKit draft and edit it. Either way, read it before you post, and make it standard.
Try our web creator to get started.
Frequently Asked Questions
What is alt text and why does it matter?
Alt text (alternative text) is a written description of an image that screen readers read aloud to users who are blind or have low vision. Without alt text, these users miss the context and meaning of images in your posts.
How long should alt text be?
As short as it can be while still doing its job. For most photos, one or two sentences is enough. Platform limits differ a lot: 1,000 characters on X, 2,000 on Bluesky, and no published limit on some platforms. See alt text character limits for each one. Our guide on how long alt text should be explains why the 125-character rule is a myth.
Should I start alt text with "Image of" or "Picture of"?
No. Screen readers already announce that something is an image, so starting with "Image of" is redundant. Jump straight into the description: "Golden retriever catching a frisbee at sunset" not "Image of a golden retriever catching a frisbee."
What about images with text in them?
Include the text in your alt text. Screenshots of posts, memes with captions, and infographics all contain text that screen reader users can't access otherwise. Transcribe the important text as part of your description.
Do decorative images need alt text?
Purely decorative images (borders, spacers, background patterns) can have empty alt text. But on social media, most images add meaning to your post and should be described. When in doubt, add alt text.
Can AI write alt text for me?
Yes. Tools like AltKit use AI to generate descriptive alt text from your images. This is especially helpful for complex images or when you're short on time. Always read the result and edit it to add context the AI might miss.
Ready to make your social posts accessible? Install the free AltKit extension and create alt text where you post.
Photo by Collabstr