Alt Text Generator for Bluesky, X and LinkedIn
This free alt text generator describes your image for people who use screen readers, then counts the result against each platform's limit so you can paste it straight in.
How it works
Upload an image and get a short and a detailed description that fit Bluesky's 2,000-character, X's 1,000-character and LinkedIn's alt text limits. The image is not stored.
Drop an image here
JPEG, PNG or WebP. It is shrunk in your browser before it is sent.
Your alt text appears here, with counts for Bluesky, X and LinkedIn.
Up to 5 images per hour. The image is not stored.
Alt text character limits on Bluesky, X and LinkedIn
Each platform caps alt text per image. The counts above measure Bluesky in graphemes, X in characters and LinkedIn in UTF-16 units, the strictest reading of each limit.
| Platform | Alt text limit | Notes |
|---|---|---|
| Bluesky | 2,000 characters | Set in the Bluesky app. Counted here as graphemes. |
| X | 1,000 characters | The limit on the media metadata endpoint. |
| 4,086 characters | API maximum. LinkedIn recommends under 120 characters. |
As of October 2026.
What good alt text contains
Alt text is what a screen reader reads aloud in place of the image. Good alt text tells a reader what they would otherwise miss.
Lead with the subject
Say what the image is about in the first words. A screen reader user hears it in order and decides fast whether to keep listening.
Skip "image of"
Screen readers already announce that it is an image. Start with the content instead. Say "screenshot" or "chart" only when the format matters.
Copy the words in the image
Headlines, captions, chart labels and the text in a screenshot are often the whole point. Transcribe them, in quotes.
Say why it is in the post
A chart needs its main trend, a product shot needs the detail you are showing off. Describe what a reader would miss without it.
Describe people, do not name them
Describe clothing, expression and what someone is doing. Add a name only when you know it and it matters to the post.
Why alt text matters on Bluesky
Many people on Bluesky add alt text to every image and expect others to do the same, and the 2,000 character limit leaves room to describe a chart or a screenshot properly. If you post the same image to X, keep the version you paste there under 1,000 characters. For LinkedIn, the short version is the one to use. Check image size before you post with the Bluesky image checker.
OpenTweet does not send alt text yet
OpenTweet posts to X, Bluesky and LinkedIn from one draft, but its composer and API do not take alt text with images today. Write it here, then add it in each app when you post.Post to Bluesky, X and LinkedIn from one draft
OpenTweet schedules posts to X, Bluesky and LinkedIn from one draft or one API call, with each version counted against its platform's limit.
7-day free trial, then from $11.99/mo. Bluesky and LinkedIn on every plan.
Alt Text Generator FAQ
What is the Bluesky alt text character limit?
2,000 characters per image in the Bluesky app. That is double X's limit of 1,000, so a long Bluesky description may need trimming before you reuse it on X.
What is the X alt text character limit?
1,000 characters per image. That is the maximum X's media metadata API documents for alt text.
What is the LinkedIn alt text character limit?
LinkedIn's API accepts alt text up to 4,086 characters per image, and LinkedIn's own documentation recommends keeping it under 120 characters. The short version this tool writes aims for that.
Is my image stored?
No. Your browser shrinks the image to at most 1,024 pixels on the long edge, sends that copy to the AI model to be described, and the result comes back to this page. OpenTweet does not save the image or the description.
Will it name the people in my photo?
No. It is told never to identify or guess who a real person is. It describes what they look like and what they are doing. If the name matters to your post, add it yourself.
How many images can I describe?
Up to 5 images per hour from one IP address, because describing an image costs more than a text tool. The limit resets after an hour.
Does OpenTweet send alt text with the images I schedule?
Not yet. The OpenTweet composer and API do not take alt text with images today. Use this tool to write it, then add it in the Bluesky, X or LinkedIn app when you post.
Related tools and guides
Bluesky Image Checker
Check images against the 2,000,000 byte limit and shrink them in your browser.
Bluesky Image Size Limit
How big a Bluesky image can be, and how many you can add to a post.
How Many Images Can a LinkedIn Post Have
Image counts for LinkedIn posts, from the app and the API.
Bluesky Limits
Every Bluesky limit in one place: posts, images, video, alt text.
Bluesky Character Counter
Count graphemes and bytes against the 300 character post limit.
Bluesky Scheduler
Schedule Bluesky posts over OAuth, with no App Password.