Alt text is a short text description you attach to an image so screen readers can tell blind and low-vision users what the image shows
Alt text (short for "alternative text") is a line or two of words you add to an image file. When someone using a screen reader encounters that image, the screen reader reads the alt text aloud instead of saying "image" or staying silent. Alt text also appears if an image fails to load, and it helps search engines understand what your images contain.
The goal is to describe what the image shows in plain language — not to label it, not to be clever, but to give someone who cannot see it the same information a sighted person gets. A photo of a golden retriever playing fetch needs alt text that says that, not "dog" or "happy moment".
How you add alt text depends on where the image lives: in a document, on a website, in an email, or in social media. The steps are different for each, but the writing part is the same.
Key Takeaways
- Alt text should describe what the image shows in 125 words or fewer, as if you were telling someone on the phone what they were looking at.
- Include important details like objects, people, actions, and text that appears in the image, but skip phrases like "image of" or "picture showing".
- Different platforms store alt text in different places: right-click properties in Word, the alt text field in Google Docs, or the image settings in social media apps.
- Decorative images that add no information to the page can have empty or blank alt text so screen readers skip them.
- If an image contains text (a sign, a screenshot, a chart), include that text in the alt text or describe what it says.
How to add alt text in Microsoft Word and Google Docs
In Microsoft Word, right-click the image and select "Edit Alt Text" from the menu. A panel opens on the right side of the screen with a text box labeled "Description". Type your alt text there. Word also shows a checkbox for "Mark as decorative" — check this box only if the image is purely visual and carries no information (like a colored line or background pattern).
In Google Docs, right-click the image and choose "Alt text" from the menu. A dialog box appears with two fields: "Title" (optional) and "Description" (where you write the alt text). You can also leave the description blank and check "Marked as decorative" if the image serves no informational purpose. Click "Apply" to save.
Both programs let you edit alt text later by right-clicking the image again. If you are sharing the document with others, the alt text travels with it — anyone who opens the file will see it, and screen readers will read it.
How to add alt text on websites and content management systems
Most websites use a content management system (CMS) like WordPress, Wix, or Squarespace to manage images. When you upload an image, look for a field labeled "Alt text", "Alt tag", or "Alternative text". Type your description there before you publish the page.
In WordPress, upload the image to a post or page, then click on it. A panel appears on the right with an "Alt text" field. Type your description and save. In Wix, click the image, then look for an "Alt text" option in the settings panel. In Squarespace, right-click the image and select "Edit" to find the alt text field.
If you manage a website and do not know which CMS you use, check with whoever set it up or look at the login page — it usually says the platform name. Most CMS platforms have built-in help or tutorials for adding alt text, and many will remind you if you upload an image without it.
How to add alt text on social media platforms
Facebook and Instagram both let you add alt text before or after you post. On Facebook, click the image in your post, then look for "Alt text" in the menu. On Instagram, tap the image, then select "Advanced Settings" and choose "Alt text". Type your description and save.
Twitter (now X) lets you add alt text when you compose a post. Click the image icon, upload your photo, then click "Add description" before you post. LinkedIn has an alt text field when you upload an image to a post — look for "Alt text for accessibility" in the image settings.
TikTok does not currently have a built-in alt text feature, though you can describe the video in the caption. If you post images to multiple platforms, add alt text on each one separately — the text does not transfer between them.
What makes alt text actually useful
The best alt text is specific and factual. If your image shows a person holding a coffee cup in a kitchen, say that — not "person" or "kitchen scene". If the image contains text (a sign, a quote, a chart label), include that text in the alt text or describe what it communicates. If the image is a screenshot of a software menu, describe what the menu shows and what options are visible.
Keep it under 125 words. Most screen readers cut off longer descriptions, and most people do not need a novel. One or two sentences is usually enough. Avoid starting with "image of" or "picture of" — screen readers already announce that it is an image, so those words are redundant.
For charts, graphs, and data visualizations, describe the main point or trend rather than every data point. For example: "Bar chart showing sales increased 40 percent from 2022 to 2023, with the largest growth in the third quarter" tells someone the story the chart is meant to show.
When to leave alt text blank
Decorative images — a colored border, a background pattern, an icon that repeats information already in the text — do not need alt text. Instead, mark them as decorative or leave the alt text field empty. This tells the screen reader to skip the image entirely, which keeps the page moving for someone listening to it read aloud.
If an image is purely decorative but you cannot mark it as such in your platform, write minimal alt text like "decorative" or "spacer". The goal is to signal that the image adds no new information.
Do not confuse decorative with "not important". A logo, a photo of a product, or an illustration that supports the text is not decorative — it carries meaning and needs real alt text.
Alt text for images that contain text
If your image is a screenshot, a poster, a sign, or anything with words in it, include those words in the alt text. If the text is short (a few words or a sentence), type it out. If the text is long (a full paragraph or more), describe what the text says and what it is about.
Example: An image of a restaurant menu needs alt text like "Menu for Tony's Diner, listing appetizers, entrees, and desserts with prices ranging from $8 to $24" rather than just "menu". A screenshot of an error message needs the actual error text: "Error message reading 'File not found. Please check the filename and try again.'"
This matters because someone using a screen reader cannot see the text in the image — they can only hear what you write in the alt text. If you skip the text, they miss information a sighted person would see immediately.
Frequently Asked Questions
How long should alt text be?
Most screen readers cut off alt text after about 125 words, so keep it to one or two sentences. Be specific enough that someone who cannot see the image understands what it shows and why it matters, but do not write a paragraph. If you have more to say, put it in the caption or the text around the image.
Should I include the word "image" in alt text?
No. Screen readers already announce "image" before reading the alt text, so saying "image of a dog" sounds like "image, image of a dog". Just write "golden retriever running through a field" and let the screen reader handle the rest.
What if I do not know how to describe something in the image?
Describe what you see as plainly as you can. You do not need to be an expert. If it is a technical diagram you do not understand, describe what you observe: colors, shapes, labels, and any text. If you are still stuck, ask someone else to look at it and tell you what it shows.
Can I use the same alt text for multiple images?
Only if the images are identical or nearly identical. If each image shows something different, each one needs its own description. Reusing the same alt text on different images confuses screen reader users because they hear the same description twice but see different things.
Do I need to add alt text to images in emails?
Yes, if the email contains important information in images. Most email clients support alt text, though the process varies. In Gmail, hover over an image and click the three dots, then select "Add description". In Outlook, right-click the image and choose "Edit Alt Text". In Apple Mail, you cannot add alt text directly, so describe important images in the email text itself.