Alt Text for Hero Banners: What 12 Live Sites Wrote
By AutoBoost Team · 2026-10-29 · 6 min read
Hero banners fail in ways other images do not. Slides share one alt text, a mobile and a desktop version can both go without, and a video background can keep a file name on its fallback image. On 29 October 2026 we requested the homepages of 139 UK charities, events and small businesses. 87 returned a full page we could read, and we looked at the hero banner or header image on each. The table lists 12 of them, with the alt text copied exactly from the HTML. We chose them to show the range, so the counts describe this table, not the whole web.
Key takeaways
- The three clearly good hero alt texts were 52 to 58 characters long. They named the subject and what it was doing, then stopped.
- Five of the ten hero alt texts that were not empty or missing said nothing about the picture. They were a file name, a code name or a placeholder.
- Slides shared one alt text, a mobile and desktop version both went without, and a video background kept a file name on its fallback image.
- The longest alt text, at 246 characters, read out the words printed on the banner. That job belongs to the page text.
Twelve hero images and what they said
| Site | Alt text | Characters | Verdict |
|---|---|---|---|
| Battersea | Leo the cat relaxing in his bed made from a cardboard box. | 58 | Good |
| Trussell | Man sat at kitchen table going through pile of bills | 52 | Good |
| Guide Dogs | Lorna walks confidently with her guide dog on a sunny day. | 58 | Good |
| Shambala Festival | A colourful nighttime concert scene with a crowd watching a band perform on a lit stage under multicoloured hanging flags and festival lights. | 142 | Fine (long, but it describes the scene) |
| Derbyshire Wildlife Trust | Puzzle pieces form a mosaic representing the Wild Peak landscape and its wildlife, with text promoting an urgent £100,000 appeal for habitat restoration, species recovery, and landscape connectivity, concluding with a "Donate now" call to action. | 246 | Fault: too long, reads out the banner text |
| PDSA | Hero banner image | 17 | Fault: describes the slot, not the picture |
| St Mungo's Church | Home Still.png | 14 | Fault: file name |
| Bluebell Railway | missing (no alt attribute on the mobile or desktop image of the first slide) | 0 | Fault: missing |
| Ffestiniog Railway | hm-bnr | 6 | Fault: code name, same alt on three different slides |
| BrewDog | Image description | 17 | Fault: placeholder text, same on two different heroes |
| Sussex Wildlife Trust | homepage slice 01 | 17 | Fault: file-style name |
| Marie Curie | empty | 0 | Fault: empty on a hero image |
One subject, one action, then stop
The three good examples have the same shape. Each names one subject, says what it is doing, and ends. "Leo the cat relaxing in his bed made from a cardboard box." gives a screen reader user what a sighted visitor takes in during the first second.
- Describe the one thing the banner is about. A hero is a single large picture. Name the person, animal or place, and the action. Trussell and Guide Dogs both manage it in under 60 characters.
- Leave out the page heading. The headline beside a hero is real text, so the alt does not need to repeat it.
- Do not read out text printed on the banner. The Derbyshire Wildlife Trust alt spends most of its 246 characters on the appeal wording and the "Donate now" button. Put that wording in the page text and keep the alt to what the picture shows.
- Drop "banner", "hero" and "image". PDSA's "Hero banner image" describes the slot, not the picture.
- Skip colours and mood unless they are the point. Shambala's 142 characters work because they say what is happening: a crowd, a band, a lit stage. The colour words are the weakest part.
Sliders, mobile copies and video backgrounds
Counted from the table, 8 of the 12 had a fault.
- Not descriptive at all: 5. St Mungo's Church uses a file name. Sussex Wildlife Trust uses "homepage slice 01". Ffestiniog Railway uses "hm-bnr". PDSA and BrewDog use "Hero banner image" and "Image description", which look like placeholders left in by a theme or a builder.
- Same alt text on different images: 2. Ffestiniog Railway repeated "hm-bnr" on all three slides we read. BrewDog used "Image description" on two different hero images.
- Missing: 1. Bluebell Railway has no alt attribute on either the mobile or the desktop version of the first slide.
- Empty: 1. Marie Curie has an empty alt on a hero image.
- Too long: 1. Derbyshire Wildlife Trust, at 246 characters.
Three of these are hero problems more than image problems. A slider repeats one fault on every slide. A mobile and a desktop version of the same banner means two images to fix, as at Bluebell Railway. A video background, as at St Mungo's Church, still has a fallback image, and ours carried its file name.
Empty alt belongs only on pure decoration. If a hero is a pattern or a texture, empty is correct. If it shows a person, a place or a product, it needs words. We cannot tell from the HTML whether Marie Curie's empty alt is a choice, so ask what a visitor would miss.
Length gave a warning too. Of the 10 alt texts that were not empty or missing, the lengths ran from 6 to 246 characters, with a middle value of 34.5. Five of the six faults with text were 17 characters or fewer. The good three were 52, 58 and 58, which is one short sentence. A target of roughly 40 to 100 characters is our reading of this small table, not a rule from the standard.
Tip: audit the slot, not just the image
Hero and header images are easy to miss because they often sit in a theme, a slider or a page builder block. Open your own homepage, then check each slide, the mobile version and any video fallback. If the alt is a file name or a placeholder, replace it with one plain sentence about the subject. Brand marks and small symbols need different handling, which our guides to logo alt text and icon alt text explain. The main guide to bulk alt text covers the posts side.
The free AutoBoost SEO plugin links your WordPress site to the AutoBoost SEO app, which writes missing alt text for the images in your posts in bulk. You approve each one, and it saves to the post and the media library.