Every image you publish has two audiences: people who can see it, and people who can’t. Readers who use screen readers, people on slow connections where images fail to load, and search engines all depend on the same thing to understand your pictures: alt text. It’s a short written description attached to an image, and writing it well takes less time than most people think.
This guide covers what alt text for images is, how to write descriptions that actually help, when to leave alt text empty, and how to add it in HTML, Markdown and common blogging tools.
What Alt Text Is and Why It Matters
Alt text (short for “alternative text”) is the alt attribute on an image element. In HTML it looks like this: <img src=”beach-dog.jpg” alt=”Golden retriever running along the shoreline at sunset”>. Visitors who can see the image never notice it. Everyone else depends on it.
- Screen reader users hear the alt text read aloud in place of the image. Without it, they may hear nothing at all, or just the file name, such as “IMG underscore 4021 dot jpg.”
- Readers with broken or blocked images see the alt text in the empty space where the picture should be, which at least tells them what they’re missing.
- Search engines use alt text as one signal for understanding what an image shows and how it relates to the page.
Accessibility guidelines such as the Web Content Accessibility Guidelines (WCAG) ask that meaningful images have a text alternative. Beyond compliance, it’s simply good writing: the description makes sure your message comes across no matter how someone experiences your page.
How to Write Good Alt Text
The best way to approach alt text is to imagine describing the image to a friend over the phone, in the context of the article they’re reading. Here are the principles that make that description useful.
Describe what matters in context
The same photo can need different alt text depending on why it’s on the page. A picture of a woman holding a camera in a park might be described as “Photographer adjusting the lens on a mirrorless camera” in a gear review, but as “Afternoon light filtering through oak trees in a city park” in an article about shooting in golden hour. Ask yourself: why did I include this image? Then describe the part that answers that question.
Be specific, not vague
“Dog” tells a listener very little. “Golden retriever puppy chewing a red rope toy” paints a picture. Include details that carry meaning, like the subject, the action, the setting and notable colors, but skip ones that don’t add anything.
Keep it concise
A common rule of thumb is to keep alt text to roughly one sentence, often around 125 characters or fewer. There’s no strict technical limit, but long descriptions are tiring to listen to. If an image genuinely needs more explanation, put it in the surrounding text or a caption where everyone can read it.
Skip “image of” and “picture of”
Screen readers already announce that an element is an image, so starting with “image of” just repeats information. The exception is when the medium matters, for example “Watercolor painting of a lighthouse” or “Screenshot of the export settings panel.”
Don’t stuff keywords
It’s fine if your alt text naturally includes a phrase you’d like the page to rank for, but cramming in keywords makes the description useless to the people who rely on it. Write for humans first; search engines are getting better at recognizing descriptions that read naturally.
Alt Text Examples: Weak vs. Strong
Seeing a few side-by-side comparisons is the fastest way to build the habit.
- Weak: “food”
Strong: “Bowl of ramen topped with a soft-boiled egg, scallions and sliced pork” - Weak: “photo of our team happy at work”
Strong: “Four coworkers laughing around a whiteboard covered in sticky notes” - Weak: “best hiking boots waterproof hiking boots cheap boots”
Strong: “Brown leather hiking boots standing in a shallow mountain stream” - Weak: “IMG_0912.jpg”
Strong: “Before-and-after comparison of an underexposed landscape and the edited version”
Notice that the strong versions aren’t much longer. They just choose more meaningful words.
When to Leave Alt Text Empty
Not every image needs a description. Purely decorative images, like background flourishes, divider lines or a stock photo that adds mood but no information, should have an empty alt attribute: alt=””. This tells screen readers to skip the image entirely, which saves listeners from hearing irrelevant descriptions.
There’s an important difference between an empty alt attribute and a missing one. If the attribute is missing altogether, some screen readers will fall back to reading the file name aloud. So for decorative images, include the attribute but leave it blank.
The same applies when an image is fully described by nearby text. If a caption directly beneath a photo already says “Our booth at the spring craft fair,” repeating that exact sentence in the alt text means screen reader users hear it twice. In that case you can keep the alt text brief or add only what the caption leaves out.
Special Cases: Links, Text, Charts and Products
Images used as links or buttons
When an image is clickable, its alt text should describe where the link goes or what it does, not what the image looks like. A magnifying glass icon that opens search should have alt text like “Search,” and a logo that links home might be “Home” or your site name followed by “home page.”
Images that contain text
If an image includes words that matter, such as a quote graphic, an event flyer or a sale banner, put that text in the alt attribute. Better still, consider presenting important text as real HTML text, which is easier to read, translate and search.
Charts, graphs and infographics
Complex visuals rarely fit into one sentence. Use the alt text to summarize the main takeaway, such as “Bar chart showing monthly blog traffic rising steadily from January to June,” and provide the detailed data in a table or paragraph nearby.
Product photos
For online stores, describe the details a shopper would want to know: color, material, angle and any distinguishing features. “Navy canvas tote bag with tan leather handles, shown from the front” is far more helpful than the product name alone.
How to Add Alt Text Where You Publish
Alt text belongs to the page where the image is displayed, not to the image file itself. That means the same hosted image can have different alt text on different pages, which is exactly what you want when the context changes.
- HTML: Add the attribute directly to the image tag: <img src=”https://example.com/photo.jpg” alt=”Your description here”>.
- Markdown: The description goes inside the square brackets: . Leaving the brackets empty produces an empty alt attribute.
- BBCode (forums): Support varies by forum software, so check whether your forum allows an alt option on the image tag. If not, describe the image in your post text.
- WordPress and similar platforms: Look for an “Alt text” or “Alternative text” field in the image block settings or media library.
- Social media: Most major platforms offer an option to add a description when you upload an image, often under an “Alt text” or accessibility setting.
If you host images with a service like ImageCoast and embed them on your blog, forum or store, you’ll add the alt text in the embed code on your own page. Before pasting an embed snippet, take a few seconds to fill in a description so the image is useful to everyone who visits.
A note on the title attribute: it’s not a substitute for alt text. Title text usually appears only as a hover tooltip, which doesn’t help touchscreen users and isn’t read consistently by screen readers.
A Quick Alt Text Checklist
- Does the image convey information? If not, use an empty alt attribute.
- Does the description explain why the image is on this page?
- Is it specific enough to picture, and short enough to hear comfortably?
- Did you skip “image of” unless the medium matters?
- If the image is a link, does the alt text describe the destination or action?
- If the image contains important text, is that text included?
- Does it read naturally, without stuffed keywords?
Building this into your publishing routine takes a minute per post and makes your content work for every reader. Whether you’re embedding photos from ImageCoast or uploading straight to your site, good descriptions are part of publishing images well.
Frequently Asked Questions
How long should alt text be?
Aim for a single clear sentence. Many writers keep it around 125 characters or fewer as a rule of thumb. If an image needs more explanation, add it to a caption or the body text.
Does alt text help with SEO?
Alt text is one of the signals search engines use to understand images and how they relate to your page. Accurate, natural descriptions help; repeating keywords does not.
Should every image have alt text?
Every image should have an alt attribute, but decorative images should have an empty one (alt=””) so screen readers skip them. Images that carry meaning need a real description.
Is a caption the same as alt text?
No. A caption is visible to everyone and usually adds context, while alt text replaces the image for people who can’t see it. They can work together, but avoid making them identical.
Can I add alt text to an image file before uploading it?
Alt text is set on the web page or platform where the image appears, not stored in the file for display. Some photo apps let you add descriptions in metadata, but websites generally won’t use them as alt text automatically.