Alt Text Character Limit: Every Platform Compared
Short answer: HTML and WCAG set no maximum length for alt text, but keeping it under about 125 characters is the common best practice; platform fields then add their own hard caps, from 100 characters (Amazon A+ image keywords) to 2,000 (Bluesky).
Alt text limits by platform
| Platform | Hard limit | Recommended / notes | Source |
|---|---|---|---|
| HTML / WCAG | No limit | Keep it concise; ~125 characters is common guidance (e.g. Shopify, Wix) | W3C alt decision tree |
| X (Twitter) | 1,000 characters | Per image; not available for videos | X/Twitter Help (archived) ; Illinois State |
| 1,000 characters (API) | Help Center lists no in-app limit | Instagram Graph API – IG User Media | |
| 4,086 characters (API) | LinkedIn recommends under 120 | LinkedIn Images API | |
| 500 characters | Standard and video Pins | Pinterest Help | |
| No published limit | Meta recommends 125 characters or fewer | Meta: Using Alt Text | |
| Bluesky | 2,000 characters (graphemes) | App-level cap for images, GIFs, video | Bluesky app source |
| Shopify | 512 characters | 125 or fewer recommended | Shopify Help |
| Etsy | 250 characters | Listing photo alt text (same cap in the Open API) | Etsy Help ; Etsy Open API changelog |
| Amazon (A+ Content) | 100 characters | "Image keywords" field, required per A+ image | Amazon A+ Content Best Practices (PDF) |
| Wix | No published hard limit | Wix recommends max 125 characters | Wix Help |
| Squarespace | 200 characters (product images) | No cap published for image blocks; Squarespace suggests 150–200 characters | Squarespace Help |
| WordPress | No published limit | — | — |
Why about 125 characters?
The 125 figure is a rule of thumb, not a standard. Some older screen readers were said to cut off alt text around that length, and longer descriptions are tiring to listen to in the middle of a page. Shopify, Wix and Meta all recommend 125 characters or fewer, and LinkedIn suggests under 120. If an image truly needs more — a chart, infographic or screenshot of text — keep the alt short and put the full description in nearby text or a caption.
How to write alt text that fits
- Lead with the subject. "Golden retriever catching a frisbee on a beach" beats "Image of a dog."
- Skip "image of" or "picture of." Screen readers already announce it's an image.
- Include words shown in the image, like a sign, a product label or a text overlay.
- Match the context. A shop describes the product's color and material; a news site describes the event.
- Use keywords naturally. One relevant phrase helps SEO; a keyword list hurts accessibility.
- End with a period. Many screen readers pause, which sounds more natural.
What about decorative images?
If an image adds no information — a divider, background texture or icon next to a text label — give it an empty alt attribute: alt="". Screen readers will skip it. Don't leave the attribute out entirely; some screen readers then read the file name aloud instead. The W3C's decorative images tutorial covers the edge cases.
Write alt text in seconds
Not sure what to write, or need it under a platform's limit? The free Handykit Alt Text Generator looks at your image and drafts concise, descriptive alt text you can paste into X, Instagram, Shopify, Etsy or your own HTML. Review it, adjust for context, and you're done.
FAQ
What is the alt text character limit?
HTML and WCAG have no maximum length for alt text. Platforms add their own: X allows 1,000 characters, Pinterest 500, Shopify 512, Etsy 250, Squarespace product images 200, Bluesky 2,000 and Amazon A+ image keywords 100. For most images, aim for 125 characters or fewer.
How long should alt text be?
Usually one short sentence, around 125 characters or fewer. Describe what matters in the image for the page's context. Complex images like charts should get a short alt plus a longer description in the surrounding text.
What is the alt text limit on Instagram?
Instagram's API accepts up to 1,000 characters of alt text per image. The Help Center doesn't publish a separate in-app limit, so keep it short and focused.
What is the alt text limit on LinkedIn?
LinkedIn's Images API allows up to 4,086 characters and recommends under 120. Short, specific alt text works best.
Does WCAG require a maximum alt text length?
No. WCAG asks for a text alternative that serves the same purpose as the image, without a character cap. Concise alt text is a best practice, not a rule.
What alt text should decorative images have?
Use an empty alt attribute (alt="") so screen readers skip the image. Don't omit the attribute.