How to Check Image Alt Text (4 Free Ways, 2026)

You added a dozen images to a page and moved on. Months later a client asks why the site fails an accessibility audit, and the answer is sitting in the HTML: half the images have no alt attribute at all. Learning how to check image alt text takes two minutes and saves that conversation. This guide shows four free ways to do it, from a quick right-click to a full-site scan with the free Image Alt Checker from Pixellize, plus how to read the results and write alt text that actually helps.

What image alt text is and why checking it matters

Alt text (the alt attribute on an <img> tag) is a short written description of an image. Screen readers read it aloud to people who cannot see the picture, and search engines use it to understand what the image shows. If you want the full background, we wrote a separate piece on what alt text is and why it matters. This guide is about the checking part.

Why bother auditing it? Missing alternative text is one of the most common accessibility failures found every year by the WebAIM Million report (an annual scan of the top million home pages, retrieved October 2026). On the SEO side, an image with good alt text can rank in Google Images and adds relevance to the page it sits on. Both benefits need one thing: the alt attribute has to actually be there, and it has to say something useful.

How do you check if an image has alt text?

To check if an image has alt text, right-click the image, choose Inspect, and read the alt= value inside the highlighted <img> tag. That handles one image in about five seconds. For a whole page or an entire site, paste the URL into an online alt text checker and it lists every image and flags the ones with missing or empty alt.

Method 1: Inspect a single image with DevTools

The fastest check for one image needs no tool at all. Right-click the image in Chrome, Edge, or Firefox and choose Inspect (or Inspect Element). The browser opens its developer panel with that image’s <img> tag already highlighted. Read the alt attribute: text inside the quotes means alt is present, alt="" means it is empty, and no alt attribute at all means it is missing.

Keep in mind this checks one image on one page. It is perfect for a spot check, like confirming your hero image got its alt after an edit. It does not scale to a 40-image gallery, which is where the later methods earn their keep.

Method 2: Read the page source

To see every image on a page at once, view the raw HTML. Right-click an empty part of the page and choose View Page Source, or press Ctrl+U (Cmd+Option+U on a Mac). Then press Ctrl+F and search for <img to jump between image tags and scan their alt values.

Here’s the catch. Page source shows the HTML the server first sent, not what JavaScript added afterward. On a site that loads images with a slider or lazy-loads them as you scroll, some <img> tags will not appear in View Source at all. DevTools (Method 1) and a proper crawler see the rendered page, so they catch those. View Source is quick but incomplete on modern sites.

Method 3: Use a free browser extension

Accessibility extensions turn the check into one click. WAVE from WebAIM (free for Chrome and Firefox) overlays icons on the live page: a red icon marks a missing alt, a green one marks a present alt, and it tallies the errors in a sidebar. It also catches other accessibility issues, so it is a good habit for anyone building pages.

The tradeoff is scope. An extension checks the page you are currently looking at, one at a time. To audit every page on a site you would have to open each one and run it again, which gets old fast past a handful of pages.

Method 4: How to check image alt text in bulk

When you need the whole site, not one image, use a crawler. Paste a URL into the Pixellize Image Alt Checker, pick a single page or the whole website (up to 100 pages), and it lists every image with a thumbnail, its alt text, and a status badge: missing, empty, or present. You can filter to show only the problems and export the list as CSV or JSON to work through. Nothing is uploaded or stored.

To show what a clean result looks like, we ran the tool on the Pixellize home page: it found 8 images, with 0 missing and 0 empty alts, every one marked present. On a typical blog the first scan is rarely that tidy, and the filtered “missing” view plus the CSV export is what turns a vague “fix the alt text” task into a concrete checklist you can hand to anyone.

The four methods, side by side

What is the difference between missing and empty alt text?

Missing alt text means the <img> tag has no alt attribute at all, which is a real bug for both SEO and screen readers. Empty alt text means alt="" is present but blank, and that is sometimes exactly right: it tells a screen reader to skip a purely decorative image, like a spacer or a background flourish.

This is the part most “fix your alt text” advice gets wrong. Not every empty alt is an error to fill in. A decorative divider line should have alt="" so assistive tech ignores it, while a product photo or a chart must have a real description. The job of a checker is to surface both missing and empty so you can decide, image by image, which empties are intentional and which are lazy. The W3C’s alt decision tree (retrieved October 2026) is the reference for calling it.

How to write good alt text, with examples

Finding the gaps is half the job. Writing something useful in them is the other half. Good alt text describes the content and function of the image in plain language, usually under about 125 characters, without the words “image of” (the screen reader already says it is an image). Match the description to why the image is on the page.

The first time I audited a client site, a third of the images had their filename as the alt text, things like alt="DSC_0041.jpg". Every checker marked them present, so a quick pass looked clean. They were useless to a screen reader and to Google. The lesson: presence is not quality. Read a sample of the “present” values, not only the missing count.

Common alt text mistakes to avoid

• Leaving the filename as alt text. alt="banner-final-2.png" describes nothing.
• Keyword stuffing. One honest description beats a comma-separated keyword list, which can read as spam.
• Starting with “image of” or “picture of”. Redundant, since the screen reader already announces it.
• Filling decorative images with text. If it adds no meaning, alt="" is correct.
• Checking once. New uploads reintroduce gaps, so re-scan after a big content change. If an image also fails to load, run the Broken Image Checker too.

Check it once, then keep it clean

Now you know how to check image alt text four ways: Inspect for one image, View Source for a page, a WAVE extension for a page with context, and the Pixellize Image Alt Checker for a whole site with an exportable list. Pick the one that fits the job, read a few of the present values to be sure they are real, and leave decorative images empty on purpose. Run the Image Alt Checker on your site today, and you will know exactly which images need words. That, in short, is how to check image alt text, from a single tag to a full-site report.