Image alt tag checker

The alt attribute on an <img> tag is a text description of an image. Search engines cannot "see" images, so alt is the primary signal that tells Google what the image depicts — it's how images get ranked in Google Images and how they contribute to the relevance of the containing page. Alt also shows when an image fails to load and is read aloud by screen readers for visually impaired users, which affects both accessibility and user-experience signals that Google uses for ranking.

What this tool checks

• Alt attribute presence — every <img> should have an alt attribute (missing attribute is different from alt="")
• Empty alt — images with alt="" (only correct for purely decorative images)
• Filenames in alt — values ending with image extensions (.jpg, .png, .webp…) are typically auto-generated and uninformative
• Digits-only alt — values made up only of numbers or punctuation
• Generic alt — single words like "photo", "image", "logo", "banner"
• Redundant prefix — alt starting with "image of" / "photo of" (screen readers already announce it's an image)
• Very short alt — 1-2 characters, likely not descriptive
• Very long alt — over 125 characters, often keyword-stuffed or misused
• Keyword stuffing — the same word repeated 3+ times in one alt
• Duplicate alts — same alt text on multiple different images

How to write good alt tags

• Describe the image concretely — "Red bicycle leaning on a lamppost in a city park" beats "Bicycle"
• Length: a short sentence — 5-15 words, under 125 characters
• Don't start with "image of" / "picture of" — screen readers announce that the element is an image automatically
• Use keywords only when they fit naturally — don't force them in, never repeat
• For purely decorative images, use alt="" — not a missing attribute, and not a placeholder word
• Functional images (buttons, links) — describe the action, not the visual ("Submit form", not "Green button")

Good vs bad examples

Good — concrete and descriptive:

<img src="bicycle.jpg" alt="Red mountain bike leaning on a park bench">

Good — empty alt for a purely decorative divider:

<img src="divider.svg" alt="" role="presentation">

Bad — missing attribute entirely (screen reader falls back to reading the filename):

<img src="DSC_0023.jpg">

Bad — filename reused as alt, zero value:

<img src="DSC_0023.jpg" alt="DSC_0023.jpg">

Bad — keyword stuffing:

<img src="bike.jpg" alt="buy bicycle bicycle cheap bicycle online">

Bad — redundant prefix:

<img src="bike.jpg" alt="Image of a bicycle">

Common mistakes

• Missing the attribute entirely — use alt="" for decoration, a description for everything else. Omitting it is always a bug
• Using the filename as alt — CMS auto-fills like DSC_0023.jpg give search engines and screen readers nothing
• Starting with "Image of" / "Picture of" — redundant; screen readers already announce the image role
• Same alt on many different images — if every product photo has alt="product", search engines can't differentiate them
• Keyword stuffing — alt="buy bike bike cheap bike online" looks spammy and may get rewritten or discounted by Google
• Treating alt as ALT-text SEO keyword real estate — it's first and foremost an accessibility feature; SEO benefit follows from writing for users