Image Accessibility Checker

Image Accessibility Checker audits the file-level properties that shape the experience of assistive-technology users: the size of the file, the clarity of its name and the appropriateness of its format. Drop a JPG, PNG or WebP onto the page, and the tool reads those properties locally and explains, in screen-reader terms, the barrier each one represents and the correction that removes it.

Accessible images are usually discussed as a markup problem, and the alt attribute deserves that focus, but the file itself contributes just as much. A 15 MB uncompressed PNG delays the whole page for everyone, and most of all for users on slow connections, often exactly the users who rely on assistive technology. A file name like DSC_0043.jpg can be announced aloud by a screen reader as an image label when alt text is missing. A raster format at the wrong resolution either bloats the page or renders unreadable. The file and the markup are two halves of one experience.

This is the distinction from the Alt Text Checker: that tool evaluates the words you paste, while this one evaluates the picture file you drop. It is also distinct from the earlier role of the Image SEO Checker, which frames the same facts toward search performance; here every finding is framed toward the humans who use assistive technology and the participants who build the pages they read.

The report reads as a set of file facts with plain-language reasoning. Nothing is invented: the tool reports the name, weight and format it actually measured, states what a screen-reader user or a slow connection would encounter, and offers the concrete change that addresses it. There are no arbitrary risk percentages, and no single score, because accessibility problems are specific and so are their fixes.

Processing is local and modest. The file is measured in the browser, the report is assembled on the page, and nothing is uploaded; closing the tab clears the session. The practical ceiling matches the rest of the kit at about 25 MB, and the original file is never modified by the check, so you can audit a library without touching a single asset.

The workflow performs best as one stage in a larger pipeline: audit the file here, write the alt text with the Alt Text Checker, fix the name with the Image Filename Checker, then publish. Each tool owns one slice of the accessibility picture, and together they cover the ground a careful human editor would. The file-level half matters precisely because it is the half most automated publishing workflows never touch, so completing it here closes the gap that a CMS alone is not designed to close.

People who cannot see an image rely on what the document tells them about it: alt text when present, the file name as a weak fallback, and the context around it in the page. People using magnification or low-vision modes need crisp, correctly sized images that do not load so slowly that the page becomes unusable. People with cognitive or motor differences benefit from pages that render predictably and quickly.

Accessibility requirements are not a niche feature. A substantial share of visitors to any public site uses some form of assistive technology, and in many jurisdictions public and regulated content must meet accessibility standards such as WCAG. The mechanical properties of an image, size, name, format, decide whether a screen reader even gets a chance to announce something useful.

• Screen-reader users depend on alt text, with the file name as a noisy fallback when it is missing.
• Users on capped or slow connections feel every unneeded megabyte, most when the page is critical.
• Magnification users need the image to render at its real size rather than being stretched into blur.
• Teams managing content benefit from files whose names and formats are self-explanatory.

When a page publishes an image with no alt text, some screen readers announce the file name as the stand-in label. A name like DSC_0043.jpg is read aloud as a string of codes; a name like refund-policy-icon.png reads as a description. Cleaning the name is the cheapest accessibility improvement a library can make, because it silently improves every image that was ever published without alt text.

The checker reports whether the name reads as a usable label or as noise, and it frames the finding in exactly those terms: what a user with vision loss would hear if this file were the only label. The fix is a descriptive, hyphen-separated, lowercase rename applied before upload, which is the same habit the Image Filename Checker teaches from a search-angle.

Every byte an image adds to a page is a byte a visitor must download before the page is done. For users on broadband the penalty is a fraction of a second; for users on metered or congested connections, and on assistive setups that run through older hardware, the same bytes can push a page into unusable territory or blow through a data allowance. Large image files are an accessibility problem even when every other property is perfect.

The checker weighs the file against the download it represents and flags anything that no display context can justify. The fix is the standard optimization sequence: resize to the largest slot the image serves, compress appropriately, and choose a modern format. A photographic hero that arrives as a 150 KB WebP rather than a 2 MB PNG is not a trade-off, it is a strict improvement for everyone.

Raster formats impose concrete trade-offs. JPEG is efficient for photos but has no transparency; PNG is lossless and supports alpha but weighs more; WebP combines efficiency with alpha and is supported in every current browser. Serving a format because it is the habit of a tool, rather than because it fits the content, quietly punishes the users who can least afford it.

Resolution matters for magnification: an image upscaled by the layout to double its native pixels renders soft when enlarged. Shipping the image at the size its largest layout slot needs keeps zoomed views crisp, which is the property the checker rewards alongside the format check.

• Photos: WebP or JPEG, resized to the layout slot before compression.
• Logos, screenshots and transparency: PNG or WebP with alpha kept intact.
• Simple icons: SVG where a vector works, so no pixels are stretched by any zoom level.
• Master copies: archive the lossless source, serve the compressed derivative.

Accessible output is a habit, not a single edit. The pipeline is: name the file descriptively, size it to the layout, export a modern compressed format, and write a real alt text for the page. Run each image through this order before upload and the library stays accessible by construction rather than by sporadic cleanup.

The checker covers the file half; the Alt Text Checker covers the words; the Image Filename Checker covers the name with extra depth. Publish after both audits, and spot-check downloads with a screen reader once to confirm what the tools predicted. That routine turns accessibility from a checklist into a repeatable default.

• Run the Image Accessibility Checker on the file before it enters the CMS.
• Fix the flagged name, weight or format with a rename or one of the conversion and compression tools.
• Pair the result with descriptive alt text checked in the Alt Text Checker.
• Re-run the audit on the fixed file and confirm every flagged finding clears.
• Spot-check one published page with a screen reader to validate the pipeline end to end.