An alt text generator creates descriptive text for images automatically — used in social media posts, websites, and emails to help screen readers, improve SEO, and meet accessibility standards. AI-powered tools (Hootsuite's free generator, Canva, Microsoft Designer, dedicated generators) read your image and output a short description ready to paste.
Here's how alt text actually works, why it matters, what makes good alt text vs lazy alt text, and the free tools that produce quality output.
What is alt text?
Alt text (alternative text) is a short written description of an image — usually 1-2 sentences. Three main uses:
Screen readers. Visually impaired users hear the alt text instead of the image.
SEO. Search engines use alt text to understand image content. Critical for image search ranking.
Fallback. When images fail to load, alt text appears in their place.
Best free alt text generators
Tool | Free? | Strength |
|---|---|---|
Hootsuite OwlyWriter | Free | Social-media-optimised output |
Microsoft Designer | Free | Auto-generates from uploaded images |
Canva Magic Write | Free tier | Built into image editor |
SEOmagnifier | Free | Bulk image alt text |
Image2Text.ai | Free | Quick paste-and-go |
ChatGPT (with image) | Free tier | Most flexible, customisable prompts |
For social media batches, Hootsuite OwlyWriter is purpose-built. For one-off images, Microsoft Designer or ChatGPT work fast.
What makes good alt text
Specific, not generic. "Person at desk" = bad. "Woman in red sweater typing on laptop, window behind her" = good.
Under 125 characters where possible. Most screen readers truncate longer text.
Convey the relevant detail. What matters in this image for the surrounding context?
Skip "image of" or "photo of." Screen readers already announce that.
Include action. What's happening — not just what's pictured.
Add emotion when relevant. Smiling, crying, focused. Helps screen-reader users feel the scene.
Alt text examples — bad vs good
Image type | Bad alt text | Good alt text |
|---|---|---|
Product photo | "Shoe" | "Black leather running shoe with white sole and red laces" |
Team photo | "Team" | "Five colleagues seated around a meeting table laughing at a whiteboard" |
Infographic | "Chart" | "Bar chart showing 2026 social media engagement: TikTok up 45%, Instagram up 12%, X down 8%" |
Decorative | "Pattern" | "" (empty alt for purely decorative — screen readers skip) |
Alt text on each social platform
Instagram: Settings → Advanced settings on each post → Alt text. Up to 100 characters.
X / Twitter: Click the image after upload → "Add description." Up to 1,000 characters.
LinkedIn: Upload image → "Add alt text" button. Up to 120 characters.
Facebook: Edit image after upload → "Override generated alt text."
Pinterest: Description field serves as alt text — write a full paragraph here.
Alt text and SEO
Image alt text is one of Google's strongest signals for image search ranking. Pages that include alt text on all images rank significantly higher in Google Images. Three SEO-specific rules:
Include your target keyword once. Not stuffed — just once, naturally.
Match alt text to surrounding content. If the page is about "vegan recipes," alt text should reference vegan + the dish, not generic photo descriptions.
Skip filename gibberish. Image-1234.jpg is fine as a filename, but alt text needs to be human-readable.
AI-generated alt text — quality check
AI tools produce solid first drafts but require editing. Common AI mistakes:
Overly literal ("a rectangular table with four chairs around it" — too verbose)
Misidentifies people (treats every man with a beard as the same person)
Misses context relevant to your post (AI doesn't know your campaign)
Generic ("a sunny day" — but the image shows a specific landscape)
Rule of thumb: AI generates draft, you edit for accuracy + context. 30-second edit per image. Vastly faster than writing from scratch.
Bulk alt text generation
For e-commerce sites + content libraries with hundreds of images:
WordPress plugins. Automatic Alternative Text, Optimole — auto-generate via AI.
Shopify apps. SEO Pro, AltText.ai — bulk-process product images.
Google Sheets + AI scripts. Custom for power users.
SEOmagnifier. Upload CSV of URLs, get alt text back.
Why accessibility matters
About 15% of the global population lives with disabilities. Around 250 million people have severe visual impairment. Alt text isn't just nice-to-have — it's the difference between including those users and excluding them.
Beyond ethics, alt text is increasingly a legal requirement. ADA (US), EAA (EU), and similar regulations require accessibility for digital content. Compliant alt text on all images is the cheapest form of accessibility coverage available.
FAQ
What is an alt text generator?
A tool — usually AI-powered — that reads an image and writes a short description for it. The output goes into the alt text field on social media posts, websites, and emails.
Are alt text generators free?
Yes. Hootsuite OwlyWriter, Microsoft Designer, Canva, and ChatGPT all offer free alt text generation.
Is AI-generated alt text good enough?
For first draft, yes. For final, edit it. AI misses context and occasionally describes the wrong thing.
How long should alt text be?
Aim for 125 characters or less. Long alt text gets truncated by screen readers + most platforms cap the field.
Should I include keywords in alt text?
Yes, once, naturally. Stuffing kills SEO + accessibility. One target keyword integrated into a clear description = ideal.
Next steps
Add alt text to every image you post this week. Use a generator for first draft, edit for specificity. For deeper coverage, read Instagram SEO strategy, share of voice in SEO, and social media content marketing. To schedule accessible posts across platforms, use the So-me Studio scheduler.
