Image sizes, cropping & alt text

Understand how WordPress handles image sizes and cropping, and learn how to write good alt text for accessibility and SEO.

When you upload an image to WordPress, a few things happen automatically. WordPress creates several smaller copies of the image for different uses — and it's helpful to understand why. This guide also covers alt text, which makes your images accessible to everyone.

Quick summary

WordPress automatically generates multiple sizes of every uploaded image: thumbnail, medium, large, and full. You can crop an image in the media library's image editor. Alt text is the written description of an image — accessibility depends on it and it helps with SEO. Add alt text to every image that carries meaning.

Why WordPress creates multiple image sizes

When you upload a photo, WordPress doesn't just store the original. It creates several copies at different dimensions. This allows WordPress to show the right size for the right context — a small thumbnail in a blog list view, a medium image inside a post, and a large image in a gallery.

The default sizes WordPress creates are:

Size name	Default dimensions
Thumbnail	150 × 150 px (cropped to square)
Medium	Up to 300 × 300 px
Medium Large	Up to 768 px wide
Large	Up to 1024 × 1024 px
Full	The uploaded file, or a scaled-down copy (2560 px at most) if the original is bigger than that

For large uploads, WordPress also makes copies up to 1536 × 1536 px and 2048 × 2048 px. Your theme and any page builder plugins may register additional custom sizes.

Storage tip

All these copies take up disk space. This is normal and expected. If storage becomes an issue, a plugin can clean up unused size copies — ask us if you need help with this.

How the thumbnail crop works

Of WordPress's own sizes, only the thumbnail is cropped (from the center of the image), unless someone has turned that option off in Settings → Media. The other built-in sizes scale proportionally without cropping. Themes and plugins can add sizes of their own that are cropped.

If your image has an important subject — a person's face, a product — that's not in the center, the thumbnail may cut it off. The simplest fix is to crop the image so the subject is centered, or upload a version that's already framed the way you want. You can crop in WordPress:

Go to Media → Library in your dashboard and click the image you want to adjust.

Click "Edit Image" in the attachment details panel. This opens the image editor.

Draw your crop area by clicking and dragging on the image, then click Crop above the image to apply it.

Click "Save Edits." WordPress regenerates the image sizes from your cropped version.

The crop applies to every size

The image editor applies your edits to all sizes of the image. Since WordPress 6.3, the option to crop only the thumbnail is hidden unless a developer turns it back on. Edits aren't permanent: you can restore the original image later from the same editor. If you need a different crop just for thumbnails, ask us.

What is alt text?

Alt text (short for "alternative text") is a written description of an image. It serves two important purposes:

Accessibility — Screen readers (used by visually impaired visitors) read the alt text aloud instead of showing the image. Without alt text, those visitors have no idea what the image is.
SEO — Google uses alt text, along with computer vision and the rest of the page, to understand what an image shows. Good alt text helps your images appear in Google Image Search.

Alt text is required, not optional

Missing alt text makes your site less accessible and less findable. WordPress will let you publish without it, but you should add it to every image that carries meaning. If you need to add alt text to many existing images, we can help audit and update them.

How to write good alt text

Good alt text describes what the image shows, concisely and specifically.

Ask yourself: "If this image didn't load, what would a visitor need to know?"

Situation	Poor alt text	Good alt text
Team photo	"photo"	"Three women working together at a conference table in a bright office"
Product shot	"image1"	"Blue ceramic coffee mug with a brushed copper handle"
Decorative divider	(any text)	Leave blank — decorative images get empty alt text
Logo	"logo"	"Maple Street Bakery logo"
Chart	"chart"	"Bar chart showing a 40% increase in sales from 2023 to 2024"

Keep it short. A short phrase or sentence is usually enough. If an image needs a longer explanation, put it in the caption or the page text.

Don't start with "Image of" or "Photo of" — screen readers already announce it as an image.

Decorative images get empty alt text. If an image is purely decorative (a background texture, a divider line) and adds no information, leave the alt text field blank. This tells screen readers to skip it.

How to add or edit alt text in WordPress

Go to Media → Library in your dashboard and click the image you want to update.

Find the "Alternative Text" field in the detail panel on the right side of the screen.

Type your description into the field.

Click outside the field. WordPress saves the change automatically and shows "Saved."

This alt text becomes the default for places you insert the image from now on. Images already placed on a page or post keep the alt text they had when you inserted them, so update those in the page editor: the Image block has an Alternative text field in its settings panel.

What image dimensions should you upload?

Uploading a 6000 × 4000 px photo from your camera is unnecessary — WordPress will scale it down anyway, but it keeps the large original on your server too. A good rule of thumb:

Full-width banner images — 1920 px wide at most
Content images — 1200 px wide is usually plenty
Logo — match the size you want it to display, or ask us for guidance

See image basics for your website and how to compress images for more on preparing images before you upload.

Common questions

I changed the alt text but it still shows the old text in Google. Why?

Two things to check. First, if you changed it in the media library, the image already on your page may still have the old text (see above). Second, Google has to recrawl and reprocess your page to notice changes, which Google says can take a few days to a few weeks. This is normal.

Does the caption affect SEO the same way as alt text?

The caption is visible text shown below the image on the page — it helps readers and adds context. Alt text is mainly for screen readers and search engines (browsers also show it if the image fails to load). Both matter, but they serve different purposes. Use both when they add value.

Can I change the default image sizes WordPress creates?

Yes — from the dashboard, go to Settings → Media. You can adjust the maximum dimensions for Thumbnail, Medium, and Large sizes. WordPress uses these sizes when an image is added to the Media Library, so changes apply to new uploads. For existing images, you'd need to regenerate sizes, for example with a plugin. Ask us if you need help.

My image looks blurry. Why?

This usually means WordPress is displaying a smaller copy than you'd like, or the original image wasn't large enough. Try uploading a higher-resolution version. If the issue persists, it may be a theme or block setting — contact us and we'll take a look.

Need a hand?

If you're stuck, email support@chykalophia.com and we'll help. Include your website address and a screenshot if you can.