# Alt text generator Upload an image and get alt text for screen reader users, with a shorter alternative, or write your own with the checklist. We don't keep your image. ## Alt text that says what matters People who use a screen reader hear your post instead of seeing it. Alt text is how they get the image: who or what is in it, what is happening and any words it shows. The generator looks at your image and writes one alt text within the length you choose, plus a shorter alternative for networks or posts where less is better. It follows the W3C's advice for text alternatives: describe the image's purpose as concisely as possible, put the most important detail first and leave out words like "image" or "picture". Text inside the image, such as a headline on a graphic, is copied word for word. If the AI part is switched off, the checklist on this page works the same way. ## Tips for better alt text - Write for the post. The same photo may need different alt text in a product launch and in a team update: add what the post is about. - Describe, don't guess. Leave out names, ages or feelings you cannot see in the image. - Keep numbers and text exact. For a chart or a quote card, include the key figure or the words. - Skip decorative images. An image that adds nothing to the message can have empty alt text. - Check before you post. AI can misread small details, so read the result against the image. ## From alt text to a published post Alt text belongs to the image you post. In PostBoost you can add alt text to each image in the composer, write it with AI, check the image sizes for every network and schedule the post to all of them from one calendar. ## How to use 1. Upload the image you want to post: a JPEG, PNG, WebP or GIF (the first frame), up to 1 MB as a guest or 5 MB with a free account. 2. Choose Short (up to 125 characters) or Detailed (up to 250), and add what the post is about if the image needs context. 3. Select Write alt text to get one alt text and a shorter alternative, each with its character count. 4. Check that the text matches the image, especially names, numbers and any text in it, then copy it. 5. Paste it into the alt text or image description field of the network you post to. ## FAQ ### What is alt text? Alt text is a short written description of an image. Screen readers read it aloud to people who cannot see the image, and it is shown when an image does not load. Most social networks have an alt text or image description field when you add a photo. ### How long should alt text be? As short as it can be while still saying what matters. The W3C's guidance is the most concise description possible of the image's purpose, with the most important information first. The Short option here stops at 125 characters and Detailed at 250, for images such as charts or screenshots that need more. ### Should alt text start with "image of"? No. Screen readers already announce that there is an image, so the W3C notes there is usually no need for words like image, icon or picture. The generator leaves them out and starts with the subject. ### Do you keep my image? No. The image is read once to write the alt text and is never saved: no copy is stored on our servers, only the text result is cached so the same image gets the same answer without a second charge. ### How does the AI alt text generator work? When it is switched on, your image and options are sent to PostBoost and our AI provider, which describes the subject, the action, the setting and any text in the image. Each visitor gets a few free generations per day, shared with the other AI tools, and signed-in users spend one AI credit per new image. ### Does every image need alt text? Images that carry information do. A purely decorative image, one that adds nothing to the post, can have empty alt text so screen readers skip it. The W3C's alt decision tree helps you decide. ### Why is the upload form not shown? The AI part can be switched off, for example when the monthly free allowance is used up. The checklist still works, and a free PostBoost account lets you add alt text to images when you schedule posts. ## Related - [Social media image sizes, with a free resizer](https://postboost.co/tools/social-media-image-sizes): Image sizes for Instagram, Facebook, LinkedIn, X, TikTok, YouTube, Pinterest and more, each with its source. Crop and resize your image in the browser. - [Social media post checker: check your post before you publish](https://postboost.co/tools/social-media-post-checker): Check a post before posting: character limits, hashtags, media count, video length and see-more cut-offs for X, Instagram, LinkedIn, TikTok and more. - [Post editor](https://postboost.co/features/editor): Write once, adjust per account, preview it the way each network shows it and pick the format: Reel, Story, thread, offer, board or privacy. Last verified: 2026-10-18 ## Sources - [W3C WAI images tutorial, tips: the most concise description of the image's purpose, important information first, no need for words like "image"](https://www.w3.org/WAI/tutorials/images/tips/) - [W3C WAI: an alt decision tree (informative, functional and decorative images)](https://www.w3.org/WAI/tutorials/images/decision-tree/) Canonical: https://postboost.co/tools/alt-text-generator